New preamp or other suggestions?

I'm really getting tired of the harsh sound of my system. At this point, I honestly would rather listen to music in my car than in my listening room. I've always chalked it up to a poor room layout (and that's not something that I can change), because this same system sounded UNBELIEVABLE in the dealer's showroom. For what it's worth, I've already treated the room with Echobusters panels, which helped quite a bit, but not enough to make the system sound really enjoyable.

Recently an audiophile friend suggested that a good tube pre might make the system more listenable. The current system is:

Source 1: CAL Icon MKII HDCD w/PowerBoss power supply
Source 2: Music Hall Fidelity CD-25 (stock)
Pre - Bryston BP-20 line stage (balanced to pwr amp)
Power - Bryston 4BST
Speakers - Thiel 3.6
Interconnect (pre to pwr, bal)-AQ Lapis or Nordost Red Dawn
Interconnect (CD to pre) - AQ Lapis, unbalanced
Spkr Cable - AQ Midnite X3

The system on the whole is currently lacking mid-bass (the terrible room strikes again) and has a harsh, in-your-face high end. Of the two sources, the CAL has a MUCH better bottom end, but is lacking detail and air at the top, and has a very "forward" presentation. The CD-25 has a much more detailed (and enjoyable) top and a wider soundstage, but light bass.

I listen mostly to pop, acoustic jazz and contemporary electric jazz.

My friend suggested picking up a used AR or CJ tube pre in place of the Bryston. Another friend suggested replacing the op-amps in the CD-25 with 627's to enhance its bottom end.

I'm a musician and not an audiophle, so I don't know if the advice I've received will fix the problem.... I'm also on a budget, but could swing $1-1.5K on a new/used pre if that would fix my problem.

Do any of you experts (and I mean that sincerely) have any ideas?
I am afraid that Thiels (in your room) are at fault here. Despite my admiration for 3.6, or any Thiel model, room interaction is crucial here. Quick fix to ad a "buffer" in some form of euphonic "magic tube" is wrong way about it. That kind of approach amounts to stuffing your ears with cotton to make your system listenable. Go back to your dealer, with dimensions of your room and drawn position of your speakers and system. He will probably help you to come to some long term solution.
I had a 4B-St and I also found the amp to be harshed. I now have all Audio Research equipment. The amplifier is the VT 100 MK II and the pre-amp is the Reference 1. I would try a different amp and see what that can do.
There is absolutely nothing wrong with the Bryston preamp. It is not the source of any harshness you hear. Probably the speakers and room.
Another Agon'er that is using Thiel's recently contacted me. He was experiencing the same problems that you are i.e. lack of warmth & body and a bright and hard high end. He was using some very expensive speaker cables of good reputation that are noted for being "somewhat warm" sounding. He replaced them with Goertz MI-2's and can't believe how much better his system sounds. He told me that his system has never sounded so natural or liquid. The fact that the same length of Goertz cost him less than 1/5 the cost of his "hose sized, hi-tech" speaker cables really pissed him off to say the least. Sean

PS... I could be wrong about this, but i think that Thiel voices their speakers / uses Goertz as a reference within their systems. If you do go this route, PLEASE use Zobel networks whether you think you need them or not.
Have you explored whether the problem could be with the quality of your AC? I would highly suggest you put a PS Audio P300 or other PS model to power only your front end components (sources and pre). This completely regenerates the AC wave form from DC and removes all noise and hash. I have a Krell/Thiel set up and a P300 really helped sweeten everything. Plus the added 3D is a bonus. No harshness whatsoever now.