If you can go a little higher than $400 you might be able to add a Naiant Tinybox (depending on your mics). The pre-amp in the M10 isn't bad, but the Tinybox is much nicer.
Getting both the M10 and Tinybox into a venue isn't an issue for me. The Tinybox is about 2/3 the size of the M10.
In regards to running the M10 undercover it is the best deck I've ever used for it. My favorite feature is being able to get it recording, flip the switch to 'hold' so I can't accidentally stop the recording and still have the ability to change levels. I'll usually get it rolling 5 minutes before showtime, set my levels to close to where I think they should be and then adjust them once the band comes on. Some people are afraid their levels might get changed in their pocket, but the knob is tight enough and protected by a piece of the case that wraps around it that I've never had that problem.
The battery life on the M10 is unreal. Factor that into your cost. I can record well over 10 sets of music without changing them.