I have never heard of the Silver Gorilla brand, but the article seems to say it is made by Seasonic which is the best PSU maker. If so, then yes like that.
The 3.3v is the lowest A, followed by the 5v, followed by the 12v's which is exactly what PCs these days require from their PSUs in order to provide adequate power to the internal parts.
You could probably stand to go a lot lower on the total wattage, though. A 750w is stretching for even more power than I would probably go for.http://extreme.outervision.com/psucalculatorlite.jsp
That link will tell you about what you need for your system. I would add about 50% on top of the low value it tells you rather than 50w like it does, but that is just my personal opinion and many around here differ from it.