OCZ is a good PSU, you could look into the Corsairs modular 80plus GOLD series PSU, they're good value and keeps your bills down. Can't go wrong with it.
2 answer your first question - 700W from what manufacturer? it could be an el cheapo PSU and bow up everything inside your case. If its a seasonic, still good enough - but post back here with its details for us to be sure.
I would say that 700 W is overkill. A good 80+ (preferably Silver and up) 500-550 W PSU should be enough. I recommend a Corsair PSU because I have one and is very quiet, Seasonic PSUs are even better, but they're a little more expensive, at least where I live.
1| you'll look down a sli/crossfire barrel
2| you plan to keep your PSU inside the rig while the innards change with new tech
3| you think that, apart from the case , the PSU should last you a few builds
4| your thinking of OC'ing down the line
i won't mention capacitor aging here - though that is another point you can add