@bluethinker I own the CODA #16, owned the KRELL Duo 175XD, and demoed the Luxman.
Nothing smokes any of these components. It is a matter of your sonic preference. My favorite amp is the Benchmark AHB2, so that is a frame of reference for my statements.
The CODA comes closest to the AHB2 in terms of transparency, but it is not as clear and clean sounding as the AHB2. However, it is the second best in this regard and the best in terms of drive and power. This amp is a monster with finesse. The best overall amp I have owned.
I tried the CODA #16 with the Magnepan LRS+, KEF LS50 Meta, and now Yamaha NS5000. The NS5000 and CODA #16 is stunning. The CODA increased the bass on each of these speakers.
I need a second amp for my LRS+ and I was and still thinking of the KRELL Duo 300XD for $6250 used. Check A’gon or USAM. The only reason I have not gotten it is that it is big, and I want something smaller for my office. I have a PeachTree GAN400 coming today for the LRS+, which could work.
Reading your statements on the Luxman 509x, I would think the KRELL Duo 300XD would be a great choice for you. It is 300 watts in Class A. DOES NOT RUN HOT. it has fans but it never turned on for me with my 175XD. It is also the smoothest, and most relaxing sound I have ever had in the house. It is also very strong on the bass. I think the CODA #16 is a bit stronger, but it is a close call. I have owned the 175XD and also the KRELL 300i integrated so I know this sound pretty good. The KRELL Duo 300XD would be incredible with my LRS+ and the NS5000.
Actually, the ideal amp for my office would be something like the Luxman m900u because it has the dual zone speaker setup. I need something like that for my LRS+ and RAAL SR1a headphones. So, if my Peachtree GAN400 does not make me happy I will look at an amp with dual zone feature.
I am also thinking of a crazier plan of buying the KRELL i400 amp for my NS5000 and moving the CODA #16 with my LRS+ (amazing combo). I am trying to decide whether to put stupid money towards an expensive amp, or the expensive Playback Designs DAC, or stay the course with more affordable gear.