doug,
If you ever get a chance to listen to your IB1's with a 4B-ST /SST, or a 7B-SST, I would be interested in hearing how these amps compare (versus the 7B-ST) when mated with the IB1's. I'm currently driving my IB1's with a 4B-ST (PRO). Personally I found a big difference between the 3B-ST and 4B-ST (positive) on both small and large speakers. I'm trying to decide what my next amp upgrade will be within the Bryston family.
Thanks.