When I was looking to get an integrated amp, I demoed the Luxman 509x and it was rather good. Then I made the mistake of listening to the Luxman c900u + m900u with the Luxman DAC in the then top end Luxman SACD player. The separates are significantly better than the 509x, mainly because of the stronger power supply. I mention this because I see the m900u on the used market at lower and lower prices. The m900u can also be run in mono.
The Luxman DAC is what a lot of people consider musical. Not my taste since I like a bit less warmth but that was a great system.
I think I just motivated myself to call Mitch to see if he can improve on my Livingroom system. It is a Yamaha NS500 speaker + CODA #16 amp. The speakers are a bit too close to the front wall. The sound is great but maybe it could be better. My ceiling is over 20 feet so maybe that is why the sound is good.