If you get the right sound card, you can use the adat as a set of converters and transfer digitally to the computer via lightpipe. I don't know if that would be any cheaper than a motu unit

my tracks are ALWAYS being ruined by one little pop

Clicks and pops are usually caused by clock errors. Make sure you have the clocking set to the correct defaults.

Alesis makes the AI3 ... an 8 channel a/d and d/a converter. It streets for around $400. You will need a adat compatible card in the computer too. Anything that uses the adat lightpipe will work.

Using an old ADAT will work but you will only get conversion in one direction at a time. Also you will only get 16 bit conversion out of a Blackface and 20 bits out of an XT ...

i know once I got the clocking issues worked out I gained all kinds of confidence about trusting my gear. And the sound quality improved. Getting all that usb, firewire, blah blah working is hard at first but once you get it, I cant imagine wanting an adat anymore. And, the lightpipe transfer will have the same click and pop problems that you have now till the clocks are all happy.

My main problem with ADAT is that you are imited to 48K sampling rate, otherwise you will half your track count when going S/MUX. I'd advise going AES/EBU. Other than that, the protocol is fairly robust.

Is it going to solve your popping problem??? Probably not. You've most likey got other issues.

for cards with ADAT i/o have a look at the RME HDSP 9652 (for 3 x ADAT i/o) or the 9632 which has 1 x ADAT i/o built-in + analog, there are Sound on Sound and Computer Music reviews of these at http://www.synthax.co.uk under the reviews tab.