AcBel API4FS06 (550W ) might be a cheap and quality option, but only if you don't mind modifying it. You'll need a source of 6pin power connectors to add to it.
It's a great PSU from some Sun workstation, thousands of them got liquidated as NOS years ago so there's still a lot of new ones floating around on eBay.
It has 3 12V rails. The 2 strong ones go to the ATX 24pin and the CPU 8pin connectors (these do *not* split into 20/4pin).
The weakest 12V rail goes to the drive connectors. It's not enough juice to drive a demanding graphics card that uses two 6pin connectors, so in that circumstance, molex->6pin adapters don't really work.
It doesn't have any built-in 6pin power connectors for graphics cards. You can add them though, and solder them to one (or both) of the higher rated 12V supplies internally.
I tried to use that PSU with a GTX260 by using molex->6pin adapters and it seemed to work at first, but it started tripping overload when I played Oblivion. After I soldered some 6pin harnesses to the stronger 12V rails, then it was fine. I used it for several years, over that time upgrading to a GTX275 and then a 285. This was with a Phenom2 board, maybe more power hungry than yours but probably not by a huge amount.
I wouldn't try to run that card in a complete system with a PSU in the 300W-400W range, it would be asking for trouble unless the load is balanced just right for the PSU.
I should mention I've have had a persistent problem in this system with the PSU tripping overload on rare occasions when I switch it on. But it did the same thing (no better or worse) with all 3 of those graphics cards, 2 copies of the API4FS06 PSU, and a Delta 850W I bought later, so I don't think the API4FS06 was to blame. After trying many things I think it's a motherboard problem, not the PSU.
If you shop for used PSUs out of old brand name PCs/workstations/servers, sometimes you'll find a bargain when 100 copies of the same model get dumped on the market.
You have to be careful though to investigate if it will work in a standard ATX system and has all the connectors you need. The Delta 850W I bought was a bargain find like that which came originally from an HP, but it turned out to be slightly mis-dimensioned for an ATX case.
I got lucky because my case turned out to have a glued on piece of plastic inside that, when removed, made it a perfect fit for the fatass HP/Delta PSU.