Don, there's an awful lot of nonsense without support from audio technology floating around on the internet about separate amplifiers. The fact that you asked "how much difference", rather than "any difference?" indicates that you've probably heard a lot of this stuff. The facts are that no, there isn't any good reason for there to be audibly superior performance from one when two units are both operating within their designed power limits with flat frequency response and inaudibly low noise and distortion(typical these days even at moderate cost).
Your 3808 likely has all the maximum power output needed for listening to your Axioms at safe(to your hearing)levels. A slight increase of a dB or so in maximum output capability is meaningless; unused headroom is simply that: unused.
