Pass XP12. Tame, Anemic?

+1 for more burn in, and +1 for better RCAs. Are you using any power filtering or conditioning? Also, what speaker cables and power cables are you using?

Caglioti-

I have the XA-25 paired with the LTA-MZ2. It's a wonderful combination, eventually would like to move up to a the MZ3 or the big boy model.

I wish I could say I have paired with some Klipsch products to see how it sounds, but I haven't done it yet. I have a friend with some Heresy's, that we have discussed, mating. (could we sell the offspring?)

I have recently been experimenting with Shunyata Research venom v2 HC power cord, for the XA-25, vs the stock cable. Herb Reichert has a review that discusses the XA-25 being a little finicky with certain speaker cables. I use Zu Event Interconnects and a pair of $500.00 Audio Art speaker cables that work well. I also never turn any amp off, especially the XA-25.

I've listened to a few amps and I have never heard an amp with the kinda of texture and tone of the XA-25. I would also never imagine saying that my XA-25 was lacking Bass,... had to chuckle a little on that one. Once you get the two hooked up, I'd love to hear your opinion.

One more question, what music do you normally listen to?

You need to tame those klipsch with a tube pre. Forget the pass pre. Conrad Johnson would be sweet. 

I'd second those who've said it takes a few days to warm up. After that it sounds more musical. 

I find it transparent, lucid and dynamic, resolving low-level detail effectively whilst separating different strands in louder parts. It's low-noise, quite neutral, and musical. 

If your system doesn't lean in that direction, or that isn't your preference, you might miss its strengths.

Weakness is that it lacks a little power. 

You don't mention your front-end; as you upgraded from another preamp presumably the XP-12 is an improvement in other respects? It could be more revealing of the sources; it could be that one of the Pass Labs preamps with a bigger PS will help. 

Only one way to find out - can your dealer offer a demo, or a loan?