Moon North Collection Versus Pass Labs X350 - Which would have that liquid sound?

Luxman L-595 preamp section will utterly outperform the Yamaha’s preamp on all fronts. Have you tried this? The Moon 861 is a reference level amplifier that ought to be paired with a preamp in a similar class to show you what it is really capable of. Get the Pass Xp-22 ; it’s a full sounding pre with beautiful tonality and should really flesh out your 861- your Yamaha tone on steroids. The more gear you have laying around can cause inability to relax with what you have- always changing for the sake of different sound placing the emphasis on the gear and not the music. I’ve been there and know this equipment contagion syndrome well:) sell it all ; keep the moon, get pass preamp then reassess in a few months. 

The Luxman 595 is a bit on the bright side. When I have it as a preamp to the moon it's still bright. When I have the Yamaha as a preamp to the Moon it's normal not bright. If I kept the moon I would just get the moon 891 preamp. 

@dman777 equipment will influence your choice of music. It might not be what you like. Do it the right way - let your choice of music dictate what equipment matches best with it. Pairing a full sounding preamp with the moon amp might get you there. Pass preamp or a nice tube pre like one of the audio research choices with warmer cables could be the ticket. 
 

Try the 891 if you can. I had the 761/791 and for sure the 791 is not a warm and soft source. It is very revealing and transparent with hardly any character (neutral). The 891 might have more density, weight but if you think the Luxman is bright, tread carefully.

Just wanted to mention I heard a pair of Pass Labs monoblocks on DynAudios. Sounded dry and boring. Was not impressed.