What qualities stand out in really good solid state preamps?

@sameyers1 decooney I have only auditioned the XP-12 in my home and can’t speak to the characteristics of the higher end or older Pass models.

i agree with your observation that people sometimes upgrade only to wish they hadn’t sold or given away a piece of gear. Some folks on this forum post of having repurchased a piece they’d had before.

So true, being near Pass Labs 30m away, lots of it around here - I’ve also helped a few even try and buy a few different cables and sources and dacs instead of getting on the upgrade merry-go-round, to then see those same people jump again to nice tube preamps. I needed confirmation from the man myself that my own 6SN7 preamp would be a decent match for an upcoming Pass/Forte’ mod project I was planning. I chatted some with Nelson about this 4-5 years back, and the following year he came out with the NuTube Korg kit for those who wanted to try something else. It might be fun to find out if the XP12 could be modded some, trying that, or this, as another approach fwtw. Just batting around some other ideas.

I am a big fan of Schitt gear. My second headphone stack is Schitt based as is my main DAC for 2-channel. However, the Schitt SYS is not one of their better efforts. It is not a clean window into the music. Less is less in this case. I have my SYS gathering dust in a box somewhere.

@sameyers1 and @decooney 

I had XP-12 for a while before moving up to XP-22. The 12 is a great preamp and gives you a good dose of that natural, warm and extended Pass sound. I had it paired with XA30.8 driving Wilson Sabrina. Upgrading to XP-22 was a good step up though. By no means it’s a night and day difference because the XP-12 is already very good. But there are few major differences mostly due to the separate isolated and beefed up power supply. You get lower noise floor that allows more subtle details to come thru and become more apparent rather than being buried into the mix, better overall clarity, more authority and texture in the bass and bigger, more solid imaging with better instrument separation.
It retains the Pass Labs natural, extended and warm sound signature and the better details it conveys are never in your face. My next upgrade was going from XA30.8 to X260.8. The XP-22 scaled up no issues. 
I’m not a fan of a two box solution but I’m willing to deal with it given the sonic ROI you get. 
 

Here’s XP12 :

and the XP-22 for comparison:

@audphile1 Kudos on your upgrades. I wish they were within my budget.

Do you think the Pass XP-12 is a good fit for the OP, @hilde45 and his Pass Xa-25?

I recommended the XP-12 to @hilde45 in his other discussion. It’s an easy recommendation and synergy with XA25 isn’t even a conversation. But it all depends on the objective and what you’re trying to do.