Hi
Frontier design has some great cards to choose from http://frontierdesign.com/
8 channel adat = wavecenter/PCI
16 Channel adat = Dakota
I had the wavecenter PCI card a few years ago but my computer at the time wasn't powerful enough to use it properly so I sold it. I'm looking at the Dakota now for my new computer.
Anyway I think this is what your looking for.