your best bet is probably a USB soundcard with a digital input.
would a m-audio firewire do the trick?
Yes it would.
I've used the m-audio audiophile usb.
I now prefer my Microtrack because it does not tie up my computer, which I'd otherwise be using. If you have a lot of DATs to transfer, you will save time by doing the transfer to a CF card recorder, while you're editing/tracking/flacing the files on your computer.