Small Home Server Build

I'm interested in putting together a small multi-purpose home server. I would like it to act as a DHCP/Internet server and firewall, a network storage/media server (2GB+), and a home network dedicated game server (BF2 w/64 players specifically, but I'm interested in other titles as well but only running one title at a time). I'm not necessarily interested in it doing everything all at once but that would be ideal. I would like it to be as cheap as possible and preferably using an AMD cpu (gotta back the underdog). I'm a lot more comfortable with what to put together for a gaming rig but doing my own server is kind of a first. I prefer newegg. I guess I'm just not sure how much power is enough. Also, raid 5? Thanks to all who reply in advance. I suppose its worth mentioning but I probably won't be ready to purchase for a little while, but again, thanks for your help.