Glad to come across this thread. I have a Bryston B135 Squared that feeds into Thiel 2.7 speakers. Room is about 2000 cu ft with room treatments. Wanting a lower noise floor (can hear speaker buzz with my ear about 2 feet from the speakers), I tried out the Bryston 4B3 and a VTL TL 2.5i preamp. Sounded very nice..music had some extra solidity and the soundstage broaded compared to the B135.
I also ran the VTL 2.5i and used the B135 as an amp. Imaging and breadth of soundstage was good but lost the solidity/weight.
Finally, I ran the B135 as a pre-amp into the 4B3. While better than only using the B135, didn't quite match the TL 2.5i + 4B3 combination.
Decided to purchase the 4B3 and will likely go with VTL...although may ask to try the BP26 that's in the store before making the final call.