Amp upgrade from Bryston 4B

I currently have Thiel 3.6s main speakers driven by an older Bryston 4B amp that has been a good match. I have been considering upgrading the Bryston 4B amp to used Bryston 7B mono blocks(?) However, the Bryston 7B amps have had mixed on-line reviews. Any other recommended amp upgrade recommendations in the $5K used range that would be a good match for the current Thiel 3.6 speakers and potential future Thiel 3.7 speaker upgrades?

OTHER EQUIPMENT: I am setting up a 5.1 surround system with an existing Rotel 985 5 ch amp to drive Thiel SCS4 center and Higherplane 1.2 rear surround speakers. I am currently using an Outlaw Audio 995 processor in bypass mode for 2.1 stereo listening.