What are the weak points of Pass amps and pre-amps ?

Hi inna, I completely understand regarding cost.  I am thinking of what I believe is the least expensive amp, the XA25.

Yes, jetter, by all accounts for the price it is an excellent choice if you don't need more power and current. 
Besides various acoustic and vocal music, I listen to jazz rock, and with my current and I believe future speakers I would need more than what the Pass can deliver. That's in addition to what I said earlier. 

The Ypsilon preamp and phono preamp were driving Viva tube amps which were driving Avantgarde Trios and 3X Basshorns. Yuk! Switching out cabling from High Fidelity to GroverHuffman cabling made it listenable but still rather thin, bright and forward. Substituting Viva preamp and a custom designed tube pre-amp, wow, the sound mellowed and became enjoyable. We suspect that the phono preamp is also on the bright and forward side using a Kiseki on a Caliburn/Cobra setup. We also tried CDs. I know, Michael Fremer owns and believes the Ypsilon to be his favorite. Maybe in his system but not in the one I heard.

@inna, I don't think the X series or the XA series is "better" than the other absent the type of speaker you're trying to drive.  FYI I was all ready to purchase the XA series monos and Kent at Pass told me that the X series was better suited to my speakers, Thiel 2.4s.  The ONLY possible fault I can come up with is that there ARE solid state amps that provide bass that is tuned tighter than the Pass products although I think the X series is a little better than the XA series in that regard.  Its all speaker dependent.