Freebase Dali

This is probably the cheapest you'll come across that gives you both a mic input and an instrument input on two separate channels:

Lexicon Alpha USB Desktop Recording Studio: Shop Pro Audio & Other Musical Instruments | Musician's Friend

59.95 at Musiciansfriend.com (free shipping too)

Lexicon is a great brand, but this is obviously not their high end stuff. But I'm sure the converters aren't crap, and it's going to be at least 24bit. If you plan on using a dynamic mic with it, you'll be fine, but there's no phantom power on the unit, so if you have a condenser mic you're planning to use, you might want to go with something else.

A more expensive unit would be the Alesis IO 2. Which will run you about 100 bones. But you'll also have a bit more flexibility, and I've heard better press about that than the Lexicon.

Alesis iO2 Express Audio Interface: Shop Pro Audio & Other Musical Instruments | Musician's Friend

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