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

Never buy anything from a human that is trying to sell you something. They are way too dangerous. Chord? Are you kidding me? The difference between Pass and Curl designs is that they actually care what their amps sound like and they actually know how to listen to them on top of knowing what their customers want. Frankly, if it is art you are looking for buy a Boulder, best low distortion art out there . Oh, and if anybody thinks they have to spend that much money to get incredible sound they are out of their mind!! Besides, it is a lot more fun doing it on a budget.

I've only heard the 30.8 and the Int-60, but they were both outclassed by Perla Audio's Signature 50 integrated with Sopra 2's.  All of them leaned toward the warm side of neutral which I like w/ the Sopra's, but you could easily tell the Perla Audio integrated had superior clarity and image specificity without sacrificing density and that relaxed liquid sound that the .8 series has.  The Perla amp also uses only 5w in standby mode and never even gets warm, let alone Class A type of hot.

I also preferred an AVM integrated (not sure the model, roughly $10k range) to the comparative Pass offerings as well.

Never owned the  X or XA series amps or preamps, but have always felt the earlier Aleph series were somewhat overrated, having owned the Aleph 2/5 amps, P preamp, and Ono/X-Ono phonostages.  The Ono/X-Ono, in particular, were so mediocre sounding compared to, say, a Jeff Rowland Cadence

We all hear differently. The Pass Preamplifiers and phonos are very neutral and what ever you have upstream, you will hear be it good or not so good. the thing is I do not want my Preamplifiers to sound like anything. Lots do unfortunately.  The Jeff Rowland stuff is good but I certainly would not say it blows away the older Pass stuff.  Synergy is the key in this hobby.  The Pass, ,older or newer in the right system can sound fantastic.

I have a Pass X250.8 and it is wonderful in my system . 
I don't know where all this junk about heating a room comes from(I only wish). Yes they do run warm and you can feel some heat within a foot or so of the amp. Another great thing is the high bias class A, mine hardly ever leaves this mode.