Agree with Phaedrus. The CM Extreme 700W is not a PSU I'd ever recommend that someone go out and buy as it's not a true 700W unit and has few, if any, qualities that would cause me to recommend it. HOWEVER, you already have it, and it's certainly capable enough of providing the power necessary for the rig you speak of ... I see no good reason not to just use it.
The 600W Stealth Extreme is a marginally better unit. If I had both sitting on a desk deciding which to throw in to a build, that's probably the one I'd choose ... but it's not enough better that I would bother to take out the 700W CM unit to put it in instead ... unless it was really a crappy wiring job that I wanted to re-do anyways ... or I was just bored