M10's preamps are pretty good.... IMO, go battery box > MIC input.
Set your peak lights for -12... set levels to try to keep em peaking in the green (as close as you can). Even with 24 bit, do your best not to waste any bits.
From people smarter than me, the M10 is marketed as 24 bit.... but results are closer to 16 bits.
Start with levels set at 4 or 5 on the dial... and adjust accordingly.
Fantastic little deck!!!
........I think I met you once years ago at Toyota Park Phish maybe?? You told me that you used to run B&K's maybe??
Make great tapes man!!!