Late to this thread, but I have had a variety of Dynaudio & Bryston pairings over 25 years.
Current setup is Dynaudio Contour S5.4 (large towers) with 4BSST2 and BR20. Previously 3BSST2 and BP25/BDA2/BDP1 with same speakers.
In the past ran Dynaudio's Audience range (72 and 82 models) with first-get 3B, 4BSST.
All were great, but higher you go, better it sounds - of course.
But all in all, a great pairing, but be careful not to get an over-energized sound. You should be good with your 3B3 and tube pre - I'd love to hear that system in fact!