@OP its usually the second and third digits that matter the most the first is just the gen
ie: gt 630 is significantly worse then a 550ti, a 650ti however is a pretty decent card as well but a bit out of your budget
I agree with iceclock. In that range, a HD7770 is better. See if there are GTX650Ti cards in that range. I'm not sure I'd buy the cheapest graphics card with a given GPU though; I'd be worried about getting a poopy fan, low-quality shroud, inefficient (and potentially whiny) solid-core chokes, and otherwise a low-quality product.
Best answer selected by rader953.
also here is a link to my buid so far... I completely changed it after feedback from Kamen_BG. I'm worried about the power supply tough.
had to reduce cost in some area to get a better video card