Where do I go from here?

I agree with soix on the pre/pro "premp section" argument.  I also agree with many others that small tweaks in your system will help (such as placement, etc.)  I also see that you've covered the idea that front 3 speakers need to match as closely as possible.  However, I think that there are definitely a couple things on your equipment that you should know:

- The Marantz AV-7005 is very nice because Marantz uses discrete analog stages.  However, the 7005 uses the older version of the HDAM discrete analog circuits.  These have slow slew rates and are much warmer/slower and laid back.  The result can be sound that is too warm/slow that does not have enough attack/detail.  If you feel you are lacking attack/detail/resolution, maybe look at a newer Marantz.  The AV7702 is the cheapest pre/pro that has the new HDAM circuits.

- Soix's idea of adding a high end 2-channel preamp is a good one if you don't care much about home theater and ALSO have different sources you listen to (such as an external DAC).  If you use the Marantz AV7005 as a DAC, then adding a preamp won't give you much because you are still dependent on the Marantz for DAC/source.  It would be much better to upgrade the Marantz 7005 is this case. 

- It's great that you removed the RKB-650 distribution amp and the bi-amp configuration.  The RMB-1565 is going to be better.  However, it is Class D with a smallish power supply and it is my opinion that this amp sound rather flat and sterile.  If you really don't care much about home theater (which it sounds like), then the Parasound A21 comes to mind.  It is going to have much more punch, depth of soundstage, air and resolution than the Rotel RMB amp.  If you do want home theater quality, it looks like there is a 3 channel Parasound A31 on audiogon for $2100 (which is just above your threshold).

Another thing you could do if you feel the Marantz is a bit slow or laid back is do a fuse upgrade.  A Hi-Fi Tuning Supreme fuse will give more attack and detail to the sound, as well as improving overall solidness of the sound itself.  You will have to take off the top part of the case to see what is on the main power supply board (just behind the power cord socket).  Typically, a processor will have one fuse, usually about 1A in capacity.  You can push this to 2A if you want a bit more punch/authority in the sound.  Power cord upgrade can help as well.

It sounds like you have a plan.  The decision between tube and solid state has it's own decision process.  I would see if you could listen to some tube amps to get an idea on whether you would like them or not.  The tube amps may have a nice texture and sound, but they will likely be warmer/slower sounding than solid-state and may lack the deep punch and power of bass compared to the large power supply of the Parasound A21.  The A21 may seem lacking in the texture and bloom that tube amps have.  It depends on what you want.

sounds like the ML Motion series may be geared to be more of a "front row" perspective

I suspect that this could be caused by the ribbon tweeters of the Motion. I feel that ribbon tweeters can be bright/forward sounding.  The same character occurs on the ribbon of the Monitor Audio Gold/Platinum series speakers.  It is just too much and too forceful in the highs for my taste.  They are just a little bit too hard edged for me.  The conventional tweeters of the Monitor Audio Silver sound more natural to me.  Just my personal taste.

In this sense, the warmth of the Marantz 7005 could be beneficial here.  I would be careful of choosing the Hegel because they have very high resolution, but they can be a touch cold sounding, which might not be a good pairing with the forward sounding Motion speakers. 

The Parasound Halo integrated is good, but keep in mind that it's just a A23 amp with a larger transformer.  It's not going to match the performance of the larger A21 amp.  I have read several comments that the smaller A23 amp is a poor performer in comparison to A21.

well, the idea is to use dedicated sources (such as a DAC or a turntable) connected directly to the preamp or integrated.  In this situation, the Marantz processor would be "just another source".  You would use the Marantz as the master preamp when doing movies that require 5 channel audio.  In this situation, the left/right outputs of the Marantz would connect to the left/right inputs of the integrated (or preamp + amp).  The preamp/integrated would act as a "pass through" audio connection.

When listening to 2-channel audio, the Marantz would be completely shutdown.  The Integrated would be switched to another input, such as a dedicated DAC.  This would, theoretically, give you better sound quality because the goal would be to use a better preamp than what is in the Marantz.  In my humble opinion, I don't think the Marantz is really that bad because they use discrete HDAM analog circuits (instead of preamps).  I would also make the assumption that the preamp in the Marantz is better than the preamp in the Parasound Halo Integrated.  The Parasound integrated uses the same preamp circuit as the Parasound P5, which is based on op amps.  It's not bad, but there are definitely better preamps.

I would agree that the Parasound integrated would not be as good as the Hegel.  The Parasound Integrated is nice and it's at a great cost point if you need an integrated with all those extra features (i.e. subwoofer crossover, phono preamp input, etc.), but it's not going to be as clean/clear as Hegel. 

That being said, the Hegel is a very clean and articulate sounding integrated.  I don't know how good of a computer system you have, but I would suggest listening to some youtube videos.  Look for ones with Hegel H160 and others with Parasound A21.  Though the Hegel is extremely clean and articulate, it's my opinion that it can be slightly on the sterile or artificial side (much like Bryston used to be with their SST2 and previous series).

In my own opinion and tastes, the A21 is a much more natural sounding amp, but still has the clean sound and attack/detail.  However, it's a pure amp (not an integrated), so you'd have to use the Marantz full time for now.  You can still add a preamp in the middle for doing preamp duties on dedicated 2-channel sources (i.e. external DAC, etc.).

It is true that an integrated or a preamp/amp will likely sound much better than the Marantz pre/pro.  Even though the Marantz has discrete analog output stages, it likely uses op amps for the input stage of analog sources.

soix and I have slightly different preferences on how we would proceed in such a system.  I would probably be going after the A21 amp first.  He would suggest going integrated first.  One thing to know here is the A21 does have a much larger power supply than the Hegel H160.  With your speakers that will drop down 3 ohms in areas for the woofers, having a larger amp/power supply will help provide stronger midbass and bass body.  Not that the Hegel would be bad at all, but I've found that the amp power supply does have some heft in this area.

A21 is just one amp suggestion. There are others, like you have said (Bryston, Anthem, etc.).  All have their own sonic character that they bring. 

yes, everyone has their opinion and that review that soix copy/pasted sounds very much like a magazine review.  I actually completely disagree with it, if you are using Hegel H160 as a sample.  Maybe if he was using the older generation Hegels because they were smoother and softer sounding.  With H160 generation, they revised the preamp section and the sound is actually quite bright and exacting.  While the Parasound A21 is definitely has a good fast attack, I would not call it brighter or thinner at all!! 

Like we've said, everyone has their own opinions on what an amplifier or speaker should sound like.

That is awesome!  I’m glad the A21 is working out.  One thing you may try is to do critical listening with “Pure Direct” turned on and then turned off.  I had a scenario with a Yamaha receiver in which the Pure Direct mode sounded worse.  It was just too solid-state sounding and bright/harsh.  I think turning Pure Direct “off” basically routed the audio signal through another set of op amps, which further smoothed out the sound.  I’m not saying this will work the same way in your situation – everything is dependent on components used and system synergy, but it’s something you can try in addition to turning off Audyssey.

Here’s another thing I have found.  Digital audio that is played using HDMI cable as the source is not as good as using a digital COAX cable.  It just does not sound as good.  If you have not already done this, I would recommend you at least get a Beldon 1694A digital cable for each source (bluray, satellite, etc.) you have that can do a digital coax output.

https://www.bluejeanscable.com/store/digital-audio/index.htm

I have found these Beldon cables work excellent and are better than several other cables.  At $20 each for a 6 foot cable, it’s an excellent buy.  I always recommend minimum 5-6 foot digital cables to prevent short cable signal reflections.  You would have to pay $120-200 to get to the next level, such as Audioquest Cinnamon/Carbon or DH Labs D-750 cables.  These more expensive cables use silver-plated conductors which are better for digital pulse transmissions.

I have found that there are only two scenarios which require that you send digital audio over HDMI cable:

1. Sources that require Dolby Digital Plus (such as streaming services from Netflix / Amazon / Etc.).  For some reason, you cannot send Dolby Digital Plus over normal coax.

2. Bluray movies that use the bluray high resolution audio formats, either DTS-MA HD or Dolby TrueHD.  The only way you can play DTS-MA/TrueHD is over HDMI.

For normal old Dolby Digital and DTS, and even 2-channel PCM (which you would get when doing normal audio streaming from Pandora, CDs, etc.), it just sounds better to send this over digital coax cable instead of using HDMI for the digital audio.  You would still need to use the HDMI cable for video.

Since you would potentially need both HDMI and coax digital audio from your Samsung Bluray player, you could try doing setting up your inputs on the Marantz like this:

            [HDMI]      [DIGITAL]    [COMP]

BD          HDMI1      None          None

DVD        HDMI1      Coax1        None

I’m not sure if the Marantz will allow you to use the HDMI1 input for multiple sources, but you can try it out.  Then select “BD” source when playing bluray movies that use DTS-MA or TrueHD audio.  Select “DVD” when playing anything else (movies with normal DD/DTS, CDs, Pandora, etc.).

It's a very cheap way to potentially increase the end result sound quality.

Optical is a very poor digital interface because the LED diodes just cannot light up fast enough to make a pure square waveform pulse.  You can see the results here, if you scroll way down to the section that says "What if there is no SP/DIF output (digital out) in our CD player, only Toslink fiber optic type ?"

http://lampizator.eu/LAMPIZATOR/TRANSPORT/CD_transport_DIY.html

Digital COAX is always superior here.  Optical should only be used if you have no other alternative.  But if you must use it, try to get one of the high density glass fiber optical cables, such as Lifatec or the Wire World Supernova cable.

In my experience, fiber optic gives a very slow messy sound.  Detail is just not there.