Bryston 3b enough power to run B&W 802 Matrix series 3?

Classe is known to have good synergy with B&W and they’re frequently sold together for that reason — B&W even bought Classe back in 2001 but I believe they’re now both owned by Sound United. Here’s a nice pre and amp a bit over your budget but worth stretching a bit for IMHO.
https://www.usaudiomart.com/details/650021889-classe-cp-500-excellent-stereo-preamplifier/

https://www.usaudiomart.com/details/650009586-classe-ca-2100-stereo-amplifier/

The amp puts out 100Wpc but doubles down to 200Wpc @ 4 Ohms so should be fine. More power would likely help, but at your budget that might be tough. Hope this helps, and best of luck.

I have the B&W 803 D3 and can tell you they love power. Going from a single stereo amp rated at 150/300 w/ch 8/4 ohms to a horizontal bi-amp setup of 140/300 for mids and highs and 600/1200 w/ch for bass made a substantial difference.

The sound went from somewhat congested to effortless.

I see!!! I LOVE the forum! Thanks so much for saving a lot of headache for me!

Looking for 1 used power amp, and 1 pre amp below 2.5k, both... What do you think?

I would not pair that amp with those speakers regardless of power. They both skew to the bright side in the treble region and together may sound like nails on a blackboard. If you share your budget and the other equipment in your system you’ll get some much better recommendations here. Just my $0.02 FWIW.