The processor and RAM alone will probably get you up to 15fps on the slaves out in the world and you should be able to follow each other around through cities OK. You won't be astounded but you should go from "Crap, this hardly works" to "well, it's slow in shatt but at least it works all the time."

Also note that you can get an 8800 variant of the video card for another 20-30 bucks. Well worth it, IMO.