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

Perhaps I have the wrong model but I thought the Coda Continuum 8 amplifier is a high biased A/AB amplifier not 150 watts pure class A. With regard to whether the X series or XA series is "better," I assumed the XA would be preferred but when I talked to Kent at Pass Labs he steered me toward the X series for my speakers (Thiels)...he said the X series would be a better match. So I was prepared to spend significantly more money but I ended up with a X150.8 and its one of the most harmonically rich and detailed amplifiers I’ve ever heard. So much so I was thinking about trying one of their preamps.

@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.