I currently own the Bryston 4B-ST, and about 6 years ago owned a pair of Adcom 565 monoblocks. The amps have different power ratings on paper, but actually put out nearly identical power in real-world use. However, power output is not the only issue -- the quality of the sound is even more important, and here the Bryston is far superior to the Adcom. The Bryston also has a 20-year, transferrable warranty, which is unique in the high-end audio industry.
If money is not your major concern, I'd strongly recommend the Bryston 4B-ST over the Adcom 565's.
If money is not your major concern, I'd strongly recommend the Bryston 4B-ST over the Adcom 565's.