I already have a small Mackie mixer. I want a stone simple audio interface for it, preferably USB. The Focusrite Scarlett series (for example) is overkill; since I have a mixer (I like having a physical mixer), I don't need level controls, preamps, transformers, or anything else. Just inputs & outputs (a minimum of 4 of each) and a backend that goes into my computer.  It works just fine for simple live work as well as recording.  I have toyed with the idea of just getting a used or NOS M-Audio Delta series PCI-based setup.