While the alesis multimix could be useful for a lot of tasks, indeed is not exactly what you would need here. Plus it's known to have very poor driver implementation, I had the FW 12-channels version and I found it not really user-friendly as an audiocard, mostly because IT'S A MIXER, does not have motorized faders and you end up re-doing all levels every time you turn it on (not for me).
Mine (UA4FX) has got optical in/out, can do up to 48K/24bit (was unsure, I had to check since I stick to 44.1k/16bit) in fullduplex and it's a solid piece of HW, decently driven by AudioCore drivers natively.
Try to score it 2nd Hand. You don't really need more. BUT OF COURSE there are plenty of other equivalent solutions.
Two different URLs for you. Check the second to exacly define to yourself what you need and the first to see what I mean.
http://www.rolandus.com/products/details/758/specs/http://tweakheadz.com/guide-to-home-and-project-music-studios/PEACE