It will work nicely. It's the first time I've seen someone here use the X7 actually, and I'm pretty happy (I've recommended the X7 a few times before). Huntkey made shitty PSU's for a long time, but the X7 was an exception to their ways. It's a pretty decent piece of hardware for a pretty decent price, keeping in mind it's modular.
Cool rig, by the way. Three 6950's... :O