I firmly believe the ONLY good multiple amp situation is identically matched amps vertically bi-amped - and bi-wired. They should be as close as possible - same brand & model, with serial numbers closely matched. Any other method introduces the possibilty - no, make that the certainty - of timing errors. Tonality, rythym, and dynamics will suffer. I'm sure some people think they've heard good horizontal bi-amping, but did they ever try the same setup the other way 'round?
In a monoblock mood....
Ed.