Here are the ATI recommended power supply requirements for the ATI Radeon HD 5770 and 5750 video cards:
450 Watt or greater power supply with one 75 watt, 6-pin PCI Express® power connector recommended
600 Watt or greater power supply with two 75 watt, 6-pin PCI Express® power connectors for ATI CrossFireX™ technology in dual mode.
The recommendations are for an entire pc system.
Hardware Secrets did a detailed technical review of the power supply. There are some issues, For example Hardware Secrets noted:
"One problem with this power supply is the lack of precise information. The power supply label doesn’t mention anything about the maximum combined power we can pull from the two 12 V rails at the same time. On the product box it is written that the maximum combined current for the two rails is of 29 A (which equals 348 W), but on SilverStone website it is written that the maximum combined current for the two rails if of 36 A or 432 W."
Here is a link to the complete technical review:
http://www.hardwaresecrets.com/article/548/1
Corsair and Seasonic are two brands that have a reputation for high quality power supplies that consistently earn high marks in technical reviews. They are reliable, stable, and come with a 5 year warranty. Some of the newer models come with a 7 year warranty. Lately we've been seeing a few other brands offering some high quality units. One example would be the Antec Earthwatts and Antec TruePower New models which are a major improvement over Antec’s older psu’s like the Basiq models.