At a glance, I can't find the wattage that motor wants (or amps), so let's assume you need a battery that can supply the 100 amps your ESC can handle.
In that case, C rating x amp-hours gives you amps. (so yes, capacity of the pack comes into play).
For example, a 4000 mAh pack is 4 amp hours. If that 4000 mAh pack had a 25 c rating, then it's 25 x 4 = 100 amps the battery can supply (in theory).
So for you, make sure that your C rating is high enough so that when you multiply by the capacity, you are well over 100. Maybe shoot for 140+ or so to be safe? I know no one wants to over spend, but you don't want your battery working all that hard.
Does that help?
Hopefully others will chime in.
Last edited by Eman77; 08-20-2013 at 06:09 AM.