RE: another dumb question, how do you know
[link=http://www.rcuniverse.com/forum/m_7100376/tm.htm]basics of electric flight[/link]
basically there's info about using the weight of the plane, then finding the total watts (power) you want based on the weight, then choosing the proper battery and motor combination. get an ESC that will properly handle the battery selection (with room to spare is good).
2 meter planes in competition are limited to 10S, so appropriate ESC's are like the Castle Creations Phoenix HV85 or Phoenix ICE HV, etc.