I personally like to champion USB 2.0 over Firewire, but I think Firewire is probably best for those sorts of things. It's more mature in that field and whatnot.
The controller ports on an xbox are USB, heh
I got a 5-port USB controller on eBay for probably $25 shipped. There are also firewire and USB/Firewire combo cards for about the same price. Happy hunting.