I would have to recommend the Core 2 Duo lot as well. I just think it's better value for your buck. Also, you'll be stuck with DDR if using an FX-57.
Anyhoo, check out the CPU chart on Toms Hardware guide. You can choose two processors and a benchmarking method, and it will give you a graph of the performance with comparisons to other CPUs
http://www.tomshardware.co.uk/cpu/charts.html
By the way, games and such may not utilise both cores at the moment, but setting the affinity of all your background programs (firewall, etc), and then setting the affinity of the game to the other core (im currently using procaff to do this with Lock On), apparently is supposed to see an increase in the performance of the game. Apparently..... :)