I don't think you can run 3 with that CPU and you would certainly need 2 gigs of ram and a mid tier 7 series (7600) or better (8600+) video card to give it a try.

Edit: My version of playable and yours may be different 30+ FPS nearly all the time is my version. You can PLAY 3 with that CPU but I would not consider it suitable for PvP.

Might be best to go dual core anyway.