I went for the NuForce R9 over the Bel Canto M300. The choice was due to the sound and philosophical reasons.
I feel that the R9 sound stages better than the M300.
I like the R9 base, speed and speed to silence more than the M300.
I just like the R9 sound more than the M300, though it's very hard to describe why without waffling audiophile BS terms that never mean the same thing to two different people, though if pushed I'd say they're sweeter.
Philosophically, as I understand it, the NuForce guys have designed and built something new from the ground up, and then taken the risk of marketing it in a world where highest snobbery goes to SET amps, and second class citizens own FET amps. Bel Canto took a similar risk when they went tripath, but they still built on someone else's leg work (not in itself a bad thing, don't misunderstand me). However, I gather that the new Bels are simply IcePower modules in a box. You, or even I could put an IcePower module in a box, and it'd sound good. I'm not saying there's anything wrong with the Bels or the IcePower modules, they're very good, but if you want inovation you have to support the inovators, and at the moment that's NuForce.
In real terms, they're both good amps and you'll enjoy either. To my taste, the NuForce is just a bit better. I have a very hard time believing that changing power cords could make much difference though (perhaps it's more important in places where there's only half the propper amount of volts in the wires
