KGvet,
I was in a similar situation to yours a couple years ago when I decided to try a better amp on my NHT SW3P. The NHT SA-3 mono amp wasn't cutting it. I also considered the Bryston 7B, but opted for a 4B instead just in case I decided to do a dual sub DIY. I still haven't built it.
I'm still using the 4B, and just one channel is much better than the NHT amp. Maybe you could go with an older 7B or 7NRB which should save you some cash as opposed to getting a newer 7ST or 7SST.
Otherwise, the Crown amp idea is a good one.
Good luck.