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

Well you asked so here is my opinion. I owned for quite a while the Pass X350.5 amp and the XP-10 preamp.

The XP-10 preamp to me was average. The step up from it was the XP-20 which has 2 separate chassis, I never heard this unit but I didn't like having to use extra rack space for the units.

I compared directly the Pass X-350.5 to the newer XP-350.8. I just did not like the newer X350.8. To me it sounded much more closed in and had less treble presentation than the older 350.5. Caution either chassis gets very hot! 

Eventually, I tried an Atmosphere M-60 3.3 and sold the Pass. Today, I own the Bob Carver Raven 350 tube amps.

Each step improved my audio enjoyment as I moved away from Pass.

ozzy

Jetter, I own an XA25. It’s cheap in that it punchers wY over the specs and is brilliant.  I also own their pre XP-22.  Have had XP10 as well. Very good equipment.  There is nothing bad here.  I came from mostly Reference level CJ TUBE equipment.  

Well thanks medwardo and jahatl, you have both convinced me that the XA25 is not worth the investment.  Well that's totally not true, and in time I feel I will be purchasing one, but not for a little while yet.  Enjoy the Pass, and its all fun.  
George

Since you are interested in the difference between XA and X, call Kent English at Pass.  5308785350

I have the XP-12 which can turn on the XA60.8. The Ayre preamp couldn't. I needed that functionality.

Wayne, the designer of the preamps told me that the XP-10 cannot turn on the XA60.8. 

The combo is good to my untrained ears.

 If you are worried about the price of Pass amps and happen to have efficient speakers, try the First Watt line. Wonderful amps that won't break your bank.