classe ca-300 or bryston 4b sst for thiel 2.4

Get another CA-300 and try vertically bimaping. It just
sounds like you need some more current delivery. You've
already got what's considered to be one of the warmer
sounding amps out there. I vertically biamp with 2 ARC
D400mkIIs. Adding the second one really made a difference
as my speakers can suck current like your Thiels.

I have owned both the CA-300 and Bryston 4bsst. If you want more bass and less "bright" highs- look at different amps than these two altogether. But, I would first try driving the CA-300 with a different pre-amp than the SF.

I agree with the above post. Try a different tube preamp. That can make a large difference. Going to the Bryston is a waste of time imo.

I agree with with the observations of fellow A'goners. Keep the Classe amp and try another pre. It seems that you would be making a 'lateral' move with the Bryston. I might recommend a BAT pre., nice and warm and no harshness or brightness. Just my 2 cents...

i had a 4bsst that i sold to lower my investment in gear due to other priorities. replaced with B&K monoblocks - the 4bsst was definitely warmer and low end extenstion for day. driving a pair of Boston Lynnfield 500L's this is the best amp i had used to date. (ive had proceed, aragon, adcom, ayre and legacy...) the ayre would be the choice if it had more power - imo.
plenty of power to satisfy these inefficient speakers. i have never audiotioned a Classe in my system although i have heard good things about them. if you can save $1000 or so on the bryston i would think that is the way to go. not the absolute last word in resolution however. i heard esl makes an amp that has huge current and great sonics - maybe worth a try?