OCZ is a very reputable brand which come highly rated. Just want to clarify before recommending a PSU here... Your system's power usage, it would be much easier to give you a specific PSU recommendation knowing what the full computer specs are; CPU, graphics cards (if any), and various drives and fans
You should have enough "headroom" there to add quite a few fans, another optical drive, an SSD or two, couple of hard drives and go to to water cooling - just the addition of a second HD7970 would make a PSU upgrade necessary.
I would actually recommend a cooler master silent pro 600w which leaves room for upgrade and extra consumption if you intend to OC the system. Also this psu is better than most of the OCZ ones and gold rated in efficiency meaning it going to save you some money in the long run. If you don't have the budget to get it at least get 550w 80plus silver rated PSU.