balanced power for surrounds

Well, all amps with balanced circuitry, like most of the Balanced Audio Technology (BAT) some Audio Research, and other more expensive lines, have balanced inputs to take advantage of their balanced circuit design. But many less expensive amps (especially these days) have balanced inputs to take advantage of the noise rejection of balanced (XLR) interconnects, especially if you want to have long IC runs in order to keep the amps near the speakers, which is the best way to do it IMO.

Manufacturers' websites (like BAT and others) describe the nature of balanced circuit design.
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Bryston makes amps with balanced (and single-ended RCA - switchable!) inputs. For used equipment, check out the 3B-ST, 5B-ST, and 8B-ST for 2, 3, or 4 channels for what I consider good bang-for-buck. Your budget may differ. They are all 120 WPC into 8 ohms. The "ST" series is one generation old, the "SST" series are the latest if you want new, but there is no 3-channel or 4-channel version at that power level in the new line. I have a 5B-ST in my home theater system.

Another thing (amazing!) about all Bryston gear, is it comes with a twenty year, unconditional, TRANSFERRABLE warranty.
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Thanks for this - all good information.