PreSonus AudioBox 44VSL by MikeRivers
4x4 USB 2.0 interface with a very complete mixer for monitoring, including 3-band EQ, dynamics, and effects on each channel including the 4 "tape" returns. Channel processing can be applied (or not) to tracks being recorded.
Too many words to post (30 pages worth). Lots of detail, including descriptions of some test methods that you may find useful even if you're not interested in buying one.
Direct Download Link
You might find some other useful reviews on my web page, but this one should keep you busy for a while