Diagnose the weak link.

Yeah, I kink of knew it must be the preamp but wasn't sure how significant the preamp was on the total sound. Right now, many rock CD's are just way oversaturated and only the quiet passages are listenable. I really like Smashing Pumpkins but the CD of there's that I got from the library was so distorted and tinny as to be unlistenable. The same for many, many CD's. I'll look into the VTL 2.5 on ebay, thanks, (& Conrad Johnson too - although I wish I could find a CJ in black that would match the look of the Bryston 4B. What is folks opinion of the Bryston BP 26 by the way?

Nada Nad

Certainly the NAD pre is suspect, but your complaints make me consider whether or not the room and/or placement might not be a bigger issue.

I have a very similar set up: Sony 5400, Thiel 3.6s, Parasound Halo A-21. I recently borrowed a used Audio Research SP-17 line stage from a dealer and was very happy with the improved dynamics and cleaner bottom end (nice phono stage, too). Unfortunately, I couldn't work out a good price on the preamp, but I did find a nice deal on an SP-16, which will be here next week. Like others have suggested, I believe that adding a high quality tubed preamp is going to help a lot with your Thiel/Bryston combo.

A couple of additional thoughts from my own experience. The Thiels have a very strong mid-bass that can easily get out of control if your room isn't ideal. Placing the speakers along the long wall of my room really helped clean up the bottom end.

Also, don't expect much forgiveness from your current set up on badly recorded, over-compressed rock albums...even with a better preamp. Good luck.

"although I wish I could find a CJ in black that would match the look of the Bryston 4B"

Black and gold is a nice color combination, IMO.
Glad you’re losing the NAD.