Either way, ill get a good quality power supply like an 450w - 600w good high brand PSU like Rosewell, Corsair, Antec, etc
One thing you have to look for is the Amps on the 12v rail. it doesnt matter if its 700 watts but only gives 19 amps on the 12v, useless. But on the other hand if its like a corasir tx 450 and gives 30 somewaht amps on the 12v rail, then itll give closer to its max power and also give sufficient power to your GPU or whatever.
I suggest a 450w Corsair or a antec 500watt one. Both are about $60? but can run any single card config (well.... offcorse not insane overclocked stuff)