Sorry, I thought I had responded to this, but obviously not!

I'm not sure what your price point would be, but my general recommendation would be to look at the recommended requirements of the most graphics intensive game you own or would like to play. Sometimes it lists an older card that isn't available anymore, but it can give you a rough idea. Generally if you get a GPU that is a step higher than that you'll be able to at least meet the minimum requirements for similar games for a while.

I don't have a lot of experience with the entry level AMD cards, but I would guess that anything in the Radeon 6500 or 6600 bracket would be good for low to mid level gaming. They came out last year, so pricing might be a bit better. The Radeon 7600 is the entry level mobile card in the current generation so far, and would most likely be a good option as well. As I said though, I'm not that familiar with the cards in that bracket, so I could be off the mark.