I don't have one to specifically recommend. I just thought of MOTU as a heavy audio company from back in the day. Any of their audio interfaces can integrate with software like logic pro, so I assume Final Cut would be similar?
http://www.motu.com/products/motuaudio/ultralite-mk3/ looks like a decent one. It is just an input/output interface.
There are also PCI based ones, I'm not sure if those would be better.
Just a thought. I'll see if I can find a specific card, I do know one company that has their FCP through a 5.1 setup.