I cant see the point of overclocking an already fast system so I cant say yes or no on that one.
I dont overclock as theres no point in creating unnecessary potential problems.
It will definately run the 8 and 7 series cards, individually or in SLI, subject to the PSU supporting it, which it should do as I think that you bought yours with that in mind.
You couldnt really improve on it by much at the moment MB, apart from going for a Quad Core which you wont be able to take advantage of yet or an Extreme CPU at silly money.
So it should be as future proof as anything can be these days, until the next fastest/best thing comes out.