Geforce GTX 650 Ti Boost 2GB. Be very specific that you are getting the Boost version. It is very much a GTX660 Lite, which is a rad card. The 650 Ti is more of a fast 650, which is a lot more cut down. The brand doesn't really matter, just get one with two fans so that it is quieter. The single fan designs are still noisier under load.
The Ti Boost is like $180 at Newegg of I recall? Very compelling offering.