So we won't really know until we can actually get our hands on the R9 cards, we can speculate all day about it but it's totally possible the R9 cards will completely defy all predictions, we just have no way of knowing. The 79XX cards however we do know, very well. If you want a reference 7950 or 7970, I recommend Sapphire or (if you can find a reference one from them) HIS.
You don't really need to worry about power phases if you go reference as by definition they will all be the same. Of course predictably there is an exception to this rule found in the 7950 which has 3 reference designs. There is the original 7950 reference, which is characterized by a fan in the middle, then there are two 7950s with a fan on the end like a 7970. The first of these two is what I have in my rig, which is a 7950 chip in the 7970 reference PCB and 1 more power phase than the 7950 but 1 less than the 7970. IMO this is the best cost to performance card on the market today. The last variety is the 7950 on the 7970 PCB with full 7970 power phases. These are the best 7950s, but also the most expensive, and are not much of a better value than an actual 7970.
As for the 7970Ghz edition, I could be wrong but I don't believe there is a reference version, as by definition, it is not a reference spec 7970.
As a side note, all of these cards will overclock like champs, even the base 7950, as AMD cards are just built that way.
Moving on to PSUs, the weird thing about PSUs is it's not the branding that matters, only the manufacturing company. As a rule of thumb you want to look for anything made by SeaSonic, Superflower, or Sirtec(not as good as the first two but still good), tom's has a great list that links brands and models to manufacturers. Admittedly Shilka probably knows of a few other worthwhile manufactureres, I just know the big ones.
http://www.tomshardware.com/reviews/power-supply-oem-manufacturer,2913.htmlEdited by RatPatrol01 - 10/9/13 at 7:32am