well... i was going to suggest an X2 3800+, seeing as how battlefield 2 takes advantage of dual core cpus... and theyre only about $150, the last time i saw them anyhow (neither frys nor outpost have s939 versions anymore though, i just found out)
but, i agree... if you can find a similarly priced dual core, that would be the way to go, over the FX-55
till then though... you also have the option to OC your 3000+, if you wanted to go that way too, and that would net you similar performance to the FX-55, without spending any money