fsp is a good brand. that looks to only have 22a on the 12v rail, but if you stay with a 4770 then you should be fine. In fact, I would snag that newegg deal for $95 for the 4770 that happy medium linked and just call it a day. put aside the saved $75 for your next full system upgrade, you are going to be due soon for a mobo/cpu/ram/psu.
edit: regarding the gddr 5 vs gddr3 question: 4850 has a 256 bit bus but gddr 3 ram. 4770 has a 128 bit bus (so 1/2 the bus speed) but gddr5 ram (so about twice the ram spped). The bus and memory work together to give you your total memory bandwidth, which in the case of the 4850 and 4770 should be very close to identical since the two parts cancel each other out. BTW, using 128 bit bus with gddr5 is a cheaper solution so is likely to be used by most cards in the long run. ATI uses it in all their high end cards right now, too, becasuse it allows them to control costs while still keeping good memory throughput.