Newer Bel Canto S300 versus Evo series????????

Thinking about setting up a 2 channel set up or might gop with Meridian pre for 3 channel stereo (I'd get cheap amp for 3 rear channels).If I end up with some difficult to drive speakers (am thinking Gallo Ref3's which I know can suck it up) think either Evo 2's or better yet evo6 gives me more than the 150 the S300 goes to.closer to the Ref1000's current.I wonder why the S300 does not allow for mono conversion (does it-no mentioned on Bel canto site).But wondering about those whop have heard difference between the older evo series and the new amps in terms of sound quality.Anybody help?
Thanks
Chazz