The Edirol products are NOT bit perfect, so while the UA-1D is a great tool, it will resample your DATs... Bad...
I think the cheapest bit perfect way is the Zoltrix soundcards with optical inputs. I bought one used recently here for $25, but I haven't tested it yet. But from all I've heard and read, it is a nice, cheap, bit-perfect card.
Another option, one that I use, is the optical out from the DAT player into my Nomad 3. I then dump thru USB the Nomad 3 to my computer.
Both of these are cheap, easy and bit perfect. Zoltrix cards are real inexpensive, and right now the Nomad 3 can be had with coupon for $135...
Good luck!
Terry