Requesting opinions about 4 specific amplifiers

other ideas: replace integrated with integrated?  Simaudio is wonderful stuff; Moon 641?  Also, Modwright KWH 225i (hybrid).  I suspect both would sound a little warmer than your Luxman.

Personally, I feel the Luxman 509 is a little analytical to my ears, especially with those Dynaudio speakers. I agree with those posters who recommend a tube preamp to warm things up.

I love the look of the accuphase, and people who’ve heard them seem to have great things to say about them, but they just seem overpriced in the USA. Their USA distributor seems hell bent on price gouging. It’s a shame. 

Hello @jpipes , so many choices and opinions!  While never with your speakers, I have owned and quickly sold BHK 300’s which were noisy and dull.  I have owned and sold Parasound JC1+ monos, which were also lacking on sparkle.  I have demo’d the Luxman, which, I did not prefer..  I have heard many Pass amps, which I found warm and pleasing, but not magical for me.  I have not had the pleasure of Coda or Sim / Moon or Accuphase but bet they are good.  I have had the Benchmarks in my system and I thought nothing special except small and less expensive.  For me, the clear winner was Audionet amps.  The entire line shines but the magic really comes starting with the Max amps.  These were well more resolving in a pleasant way than anything I had tried or heard.  Much more sparkle on top, but in a non fatiguing way.  Very full spectrum.  They occasionally can be seen used for around 18k, more than most discussed here but to me so worth it.  I now have my Max’s upstairs, and have the  amazing Heisenbergs in my reference system.  All here is just my opinion, but I do recommend you listen to Audionet.

I suggest you forget separates and consider the darTZeel CTH 8550 especially if you like the form factor of integrated design.  From inputs, including the world class phono stage to the outputs everything is designed to maximize purity and deliver rich music with full dynamics and  clarity.  I have churned a lot of equipment over the years and when I got the CTH 8550 I was amazed as it outperformed all the separates I'd tried including the AR reference 6 pre amp and 610T power amps, Pass Labs and so forth.  darTZeel is expensive but if you off load what you have and combine it with your budget the difference should be manageable.  The Sound Advocate did a great review including interviews with Harv Delétraz you will find interesting.  Good luck.  

British Audiophile loved Atoll integrated - in300  @ $4500 new.  tilts warm with good bass control.  For amp only, Atoll has am300 for $3900 new.  Mos-fet designs, so tend to be slightly warmer.