[suicideneil]

The 1600kv medusa is a little slow for 5s, but it would be much better on 6s- MMM esc will be happy with either, and you can gear those multi-pole motors quite high to get some more speed out of them.

The C raing on batteries is simple, once its explained properly... Basically, the C rating is a multiple of the capacity in mah, and represents the theoretical maximum output of that battery, EG:

20c 5000mah lipo can put out 100amps
10c 4000mah lipo can put out 40amps.

Batteries come with a few C ratings- continuous, sustained, peak/maximum- fairly obvious what they mean.

In general, a BL motor will run at a continous power level, drawing about 10-20amps, but you will see peaks (under acceleration and braking etc) upto 80-120 amps or so, depending on the specific vehicle setup, motor, driving conditoins, weight etc etc.

Depending on budget, a battery that can provide 80amps continuous or more is great for a 1:10 scale MT or similar. Most places give the maximum amp draw of the motor, which makes life easier when choosing batteries.

EDIT: I type too slow...