Thermaltake W0133RU ToughPower 1200W Modular Power Supply
This is why you really can't go by the overall wattage ratings. Wattage ratings include all sorts of voltages that don't matter to video cards. You need to look at how the +12V power is distributed.
Look at the TP 1200: +12V1@20A, +12V2@20A, +12V3@36A, +12V4@36A. You're sort of limited on what you can do with several uneven rails like that. If you put a 30A card on that 36A rail, you're left with 6A of unusable power. Put in a second 30A card and you've lost another 6A. Now your 1200W PSU is really only 1056W.
Now look at the Cooler Master Silent Pro Gold 1200W: +12V@98A. One big fat 12V rail means each video card will get what it needs, and there won't be any rails with wasted power.