Looking for advice, recommendations

Not sure if 70Wpc is enough for you, but if so I think the Octave v70 SE integrated fits your sonic tastes very well.  The v110 SE is $1300 more but puts out 110Wpc. 
https://www.soundstageultra.com/index.php/equipment-menu/423-octave-audio-v-70-se-integrated-amplifier

If going separates the AGD Tempo di GaN amp would also be worth a look. 
 

Best of luck. 

OP,

Welcome to the forum.

From what I can tell of your system you have a great opportunity for improvement. You have very good speakers capable of much better sound than you are likely getting.

It is really helpful to us to be able to see your whole system. There is a place under your user ID to put some photos and ID your equipment. You can see ours there as well. It is really helpful.

Assuming you want as great an improvement in sound quality as possible, then I recommend spending as much as you can and buying separates. Todays integrated amps in the $10K price point are getting very good (like the Pass iNT-60), but if you desire in the long run to improve the sound quality buying used separates now are likely to get you better sound and allow smaller incremental purchases later. My rule of thumb is to always invest 2x or more in any particular component if you want an “oh, wow… that is a lot better.”

I would recommend a used Audio Research preamp to be the center of your system. They are tubed and possess the best of both worlds: details, great imaging as well as amazing musicality. I would budget $4K to $5K.

For the amp. There are lots of good choices. I really love tube amps, but high power and tubes cost money. On the other hand, my speakers are about the same sensitivity as yours and I am powering them with 60wpc tube power and the sound is fantastic and can be played louder than I can stand. Maybe, look for a less expensive amp in the mean time until you can afford something like an Audio Research REF, Conrad Johnson or VAC.

My system started out as separates into a stereo power amp.
At some point 10 years in the power amp died and I went to tube mono blocks.

Later the preamp was replaced with a tube preamp. And later that replaced with another tube preamp.
Then the monoblock tube amps replaced with a stereo tube amp… which I feel so so about. But it is pretty good.

If you had a set of earphones/headphones it is likely easier to get the front end evaluated and dialed in.

I think my front-end was pretty good before… (ARC phono into Audible Illusions).
It is just as good now.

On a lark, I put some AIYAMA A-07 $70 power amps onto the system to evaluate them for a HT integration.  It was amazing good. The Primaluna Dialogue HP Premium power amp is better, but not by miles… and not by a lot.

Yeah I have need looking at Atmasphere mono blocks.

But I would suggest your. Path 2 is what is most clearly one that will meet the goal. So just shove in a pair of the A-07s as bi-wire/bi-amp mono blocks for now, and get the front half sorted out. Maybe that Sachs one… But the used ARC suggestion is also good.

Once that is seeming to come together, then you have a system while you figure out what to do for the power amps.

With a $6k budget and already having speakers I would be putting $5k into a used preamp, the $140 into the cheap amps, and then speaker wires and RCAs to go from the pre way out to amps sitting slope to the speakers can be done for well within the remaining budget.

Sonically, I like the sound of tubes.  I want a three dimensional sound, with well defined space around each instrument and vocalist.  Looking for more detail, without harshness. 

You get a lot of ^that^ with the speakers.
The preamp can mostly only degrade things from the source, but it is also really doing a lot, and one makes or breaks things right at the front of the signal path..

Generally the amp does not make “the magic happen”… one can only loose something (detail), or add some harshness or noise with an amp. But an amp that cannot drive the load adds a lot more :character”. But every amp adds its own sonic character to varying degrees, 

The amps generally do not make the sound that you describe, and the Benchmark and Atmasphere that you mentioned are ones that don’t add a lot extra distortion in.

Powering a SS amp with a tube pre is usually a pretty solid recipe for getting good sound. And starting at the front and moving down stream is a pretty safe and reliable way to upgrade “a chain”. Put in strong links as you identify them, and don’t worry about having a weak link or two. Working the forge and anvil, one makes a chain “one link at a time”.