[MetalMan]

2p is the designation for two cells in parallel (s=series, p=parallel).

The 9920 is rated at 99amps continuous, and a bit more for burst. But just because the batteries are rated at 120amps burst doesn't mean that the motor will be pulling that much current. The ratings on Lipos are what they suggest: A battery that is rated to handle 90amps continuously should be able to handle a sustained load of 90amps without dropping its voltage too low (below 3v/cell) or getting too hot. The burst is the same way, except that a burst is a short, high amp draw.
Just don't base the controller off of the battery you are going to use, you mainly need to factor in the motor you'll be using.