Advice? Luxman C-900u vs. Pass XP22 vs. Ayre kx5-twenty

Given your equipment I recommend an Audio Research LS28SE… or as contemporary as you can find. Audio Research makes incredibly good and natural sounding preamps that can really help capture the magic of music. It is what they are known for.

Luxman is more similar to the Pass preamp than to the Ayre. Luxman are very accentuated in the treble and bass to give the “high end sound” of lots of details (treble / sparkle) and a good dollop of bass for the kick, but is lacking in midrange so really misses out on the human voice and the more musical part of music. Pass has been getting better with midrange and rhyme and pass but will not get close to Audio Research.

Ayre, in general should be the closest to the Audio Research in overall balance in musicality… but still not there.

I have owned Pass amps and preamps for decades, I heard and own Ayre, great company. And have listener to Luxman a lot as a friend of mine sells them.

Hence my recommendation. You can see my systems under my user ID

Wow, your three choices are very distinct, and IMHO not very different in "value."

Usually those who go into Pass love the sound and are loathe to give it up. 

My suggestion from where you are is really don't buy anything you can't listen to.  You may really like a tube pre, by the way, but not AR.  Hahaha. :)

Try a used CJ. 

Either Pass XP-22 or Audio Research Ref5SE or Ref6. Good synergy with Pass amps.