I second the 7770, I got mine for what would have been $105 if I did the rebate (I forgot), but still $125 was a great price for it. Not sure what games you play but mine will just about max out gw2 (I think it's my CPU that pulls it down when I throw shadows on high), it'll max out starcraft 2, WoW of course. Those are all the games that I play.
This is the one I bought, it's one of the cheaper ones but it's great, if something locks it close to 100% it usually peak at about 58C with the fan on 55%, but usually it'll stay right around 50C and I won't hear the fan at all: http://www.newegg.com/Product/Product.aspx?Item=N82E16814127687
I would personally recommend the NVIDIA 550ti as I am using one now. I upgraded mainly for Star Trek Online and it runs on MAX settings pretty flawlessly. You may need to upgrade your Power Supply because the 550ti requires 400W or more. I had to upgrade myself to a better PSU.
The 550 ti and the 650 have nearly identical performance, the 650 is a little bit better. Between those two, I would get the cheaper one, but if you have an option, HD 7770.
The GTX 650ti will have very robust performance enhancements, but you must also take into consideration price. The GTX 550ti + GTX 650 both range from $99-$129. The GTX 650ti will range from $180-$200. Quite a price hike.