I got a gtx 460 off the toms classified ads for 80 shipped, the 1 gb 256 bit variant too, think the guy is still trying to sell the other for 75 w shipping, id jump on it!
really I think right now is a great time for someone on a small budget to buy a second-hand gpu, there are some great deals to be had out there... on toms, clist, ebay or otherwise...
otherwise your budget is not going to net you a very good (brand new) card imo
what are your full systems specs.... brand make model, and your monitors native resolution?
the 7770 would certainly be a good choice too, just not as powerful, however it will consume less power than the 460 and brand new with a warranty is never bad...
either gpu would pair well with an i3...
please list your full system specs though...