Requesting opinions about 4 specific amplifiers

Have a look at the Audia Flight Integrated Amps - FLS9 or FLS10. They have the speed and transparent quality that will bring your Dynaudios to life.

I own the C20s right now pairing with Pass labs..Pass is always good with Dynaudio...but Simaudio seems to be  the ticket  when talking Dynaudio..forget tubes with those speakers IMO..you might want to think subs as well,makes a big difference

I can only fairly comment on the Pass relative to the Luxman. I find the Pass amps to capture the midrange and rhythm and pace far better than Luxman. These two parameters are key to musicality, making Pass in this situation keep detail and bass but have a much higher musicality. The Luxman has an accentuated treble and bass which gives it a sparkly high end sound… the Pass is much closer to the real thing. Great match with DynAudio… I have heard both Luxman and Pass with these great speakers multiple times.

I have owned enough Sim moon equipment… but not an amp to recommend Pass over them if my description of Pass is appealing to you. 

You might look into Coda amps, or an Anthem P2 power amp

Get the sim! It will be magic with your dyns. 
 

Keep the 509. It’s an excellent unit with an underrated preamp section. IMHO a very different choice than the Pass or Parasound. I just don’t like Pass, and Parasound tends to be too warm and laid back.

Of those you mention which I've heard, Ayre may be significantly different enough and good enough to be worth a switch to.

Consider your room acoustics.

Sounds like you’re maybe missing a bit of magic and soul in the music.  I think your instinct of trying a tube preamp is excellent, and pairing that with something like a Class A amp could deliver a lotta soul and magic.  Here are a couple excellent pieces available now just for an idea and FWIW…
https://www.usaudiomart.com/details/650105469-plinius-sa-103-class-amps-amazing-powerful-class-a/

https://www.audiogon.com/listings/lisb94a5-backert-labs-rhumba-extreme-1-3-tube-preamplifier-tube

Best of luck.

@soix +1...Hegel, now Luxman....do either enable you to enjoy your tunes ? Why do they ? Why do they not ? This will help you, and us, to further assist / guide you in a direction. Consider a pair of subs, based on improving things, and you have the room physically, and for them to open up and breath......

@grislybutter -This is helpful, thank you. I found an 860A V1 on Audiomart for $5K which is a possibility in my price range.

@soix -I'd love to pinpoint sonic improvement characteristics desired, but it's hard to be aware of what is possible without more experience.

I feel like this Luxman integrated provides good imaging, but is better possible? It sounds very detailed, and maybe slightly more analytic or cool than my last integrated-the Hegel H390. Maybe I am looking for a bit more midrange warmth? Another reason to consider separates in a tube preamp.

Again, I am looking to this community for suggestions of what might be possible. If the Luxman is the final word in pairing with these Dynaudio's, that would be nice to learn as well. 

@mike_in_nc -Good to know. My listening space is in a basement, so a bit of a break there with the temps.

@imhififan -Thank you, great to heat this! I can be happy staying with the Luxman too if it's one of the best choices to make. It's a beautiful integrated!

Be aware the Pass amps -- even the Class AB ones -- run warm. The X150.8 is specified as emitting 370W at idle. That is heat going into your room. Tough if you're in a warm climate.

This really depends on what improvements and sound characteristics you’re looking for.  Without that critical info we’re just shooting in the dark here. 

For me, Parasound power amp didn't pair well with Dynaudio.

Simaudio is a fantastic choice but way pricier.

You will find more JC5 on the used markets than the other ones, so you could add a few other, niche brands to your list?

In my opinion the luxman power amplifier section pairs well with the Dynaudio Confidence 20.

If it were me, I'd invest in a tube preamp for more SQ impact.

Again, just my opinion.

Look for demo or 1 - 2 year old amps.  You will bring those more expensive models into your budget.   The "new car smell" is not worth paying 60% - 100% more than used.  IMHO.