I suggest want to go with Firewire if you are needing multiple channel I/O.
There is a plethora of Firewire cards available. You might also check out the M Audio Delta 1010 units. But simply do a search on firewire audio interfaces and you will get a ton of information.
You can also go to the online retailers like www.musiciansfriend.com, www.sweetwater.com, www.americanmusical.com, etc. and search firewire interfaces.
You will learn a lot more doing it that way than asking here.
WARNING! INCORRECT USING THIS FEATURES MAY CAUSE YOUR SYSTEM BROKEN!