Have a look at the
Alesis iO2.
It seems to fit your whole spec and sells generally for just under $100. I bought one (well, actually an M-Audio M Track but they're the same box with different badges) about 3 years ago for a specific project (playback only in a theatre) but since then I've found it punches well above its weight and I use it for qute a few other things, particularly location recording. The preamps are good enough that you can run them full up without undue noise--I've used them successfully with very low output dynamic mics.
The unit is USB powered, direct hardwre monitoring with a mix control, switchable line/instrument on the quarter inch inputs, etc. Their ASIO drivers seem nic and solid. MIDI in and out via the usual DIN connectors.
Anyway, worth a look.