Bridging amps vs single amp of same power

I recently picked up a bryston 3b which is slightly underpowered for my speakers.I can pick up another and get 200w ea in mono,or go for a 4B which would be 200w/channel.Is one better then the other.Price would be a little more for the pair of 3b's.I'll be driving thiel cs3.5's.
The single 4B would be a better solution for the Thiels. Bridging the 3B will limit it to 8 ohm loads, which I'm pretty sure the Thiels are not.

Note that this isn't specific to Bryston amps. If a stereo amp is spec'd for 2 ohm loads, then when bridged it would be spec'd for 4 ohm loads.
I've heard that the 4Bst is significantly better than the 4b, and the 4Bsst is one further step better. Just in case you can swing it. All the Best, Peter