Disappointment with Pass Labs - I'm looking for something else

what version of Cornwall's do you have? if its the older ones that's probably your issue they were not great at detail. if its the mk4's I'd suggest a Tube amp like the LTA linier tube audio, Finale Audio /Triode labs. Luxman is another good suggestion I'd stick with their class A amps though. 

 you do not need the power of those big Pass amps X250.8 waist of money regardless of what others here say. the heritage line are quite efficient and do not need a lot of power to come alive.

I've had Heresy 3, Cornwall 3, and now LaScala's all similar and all very good with the right amplifiers. if you have older Cornwall's i recommend you look at upgrading the crossover to bring the crossover point down to 4500hz from the 6khz you will need to upgrade the tweeter as well if you go this way. google Bob Crites for more information on Klipsch upgrades, there's others but he seems to be the most common and reasonable  pricing.  the new ones have this already. 

I've tried some M60 Atmas-phere amps and they are lovely but for high efficiency i found them a little noisy could have been tubes though.

@cal3713  is right on.  I think system building starts with the speaker choice and the room you're putting them in.  That determines so much of the sound signature you are going to live with, for the most part.  And then you need to find a great amp to mate with those speakers.

I owned the Pass XA30.8, too, and I came to precisely the same conclusion that you did.  Too over-warm and a bit vague sounding, just like a blanket was thrown over the music, IME.  It, of course, didn't sing with my primary speakers, TAD CR-1's (not a happy pairing at all, and under-powered), but I also didn't like my very high efficiency Teresonic Ingenium Silvers (the reason I tried the Pass), for the reasons you find.  And I would note that both of these speaker options come from my "up front / bit brighter" camp, which would normally be a better match for a warmer amp.  The Pass just doesn't fill the bill.

I now have a Luxman M900u, and it has the attributes you say you are seeking - - a lot of definition, wondrous soundstaging, while still retaining a smidge of warmth.  And they do have plenty of drive, their Japanese pedigree aside (where did that blanket statement above come from?!).  However, I honestly can't see it with the Klipsch.  But since you're going to throw everything up in the air with a speaker change, I've offered my amp comparison, FYI.

Just get the NAD M33 Integrated, streaming 200 wpc amp with Dirac Live room correction as well as tone controls and balance control.  Simplicity in a revolutionary, distortion free amp.

Agree with mglik- AtmaSphere and Ralph rock😎

If you are after the Pass Labs sound and you are not happy with the XA30.8 then I’d thoroughly recommend the XA25 as a cheaper alternative. I sold my XA30.8 and bought an XA25 for a similar reason to the OP. I felt that as nice as the XA30.8 was, it was too warm and it didn’t have tight enough bass. The XA25 has that Class A relaxed sound but it coupled with a lower noise floor and high levels of speaker control (lower output impedance). It also has fairly similar power output to the XA30.8 (Stereophile measured 90 watts into 8 ohms). Pure Class-A extends to about 25 watts which is similar figure to the XA30.8 from memory.
It also weighs about half as much so you won’t get a hernia lifting it (ask me how I know)......