Jorge, I had a 3B-ST with and old 0.5b pre-amp. First went the pre-amp to the A3cr pre which I liked so much, I bought the amp. They also have a great effect when used together and this may explain the improvement over the Bryston (which I liked very much, just no as much).
I have Magnepan 1.5qrs bi-wired with Analysis Plus Oval 9 and Oval 12 and use as my main source an Arcam Alpha 7se (same transport as the Alpha 9se) as transport with a Bel Canto DAC 1.1. My digital cable is a Illuminati D-60, the audio interconnects are TMC (white and yellow) and I use an assortment of inexpensive after-market power cords (all under $100 used or new when I bought them) and a Monster HTS 2000 surge protector.
While the A3cr is not a devastating amount of power, I find it ample. There is a limit to how loud the Maggies can get. I have heard of many people who succesfully bi-amp the A300 and an A3cr, they are apparently gain matched (most use the A3cr for the bass)