Using a lipo you are probably going to want to go brushless. I have not ventured into the brushless realm as of yet, you will also need a brushless ESC if you go that way.

http://www.towerhobbies.com/electric/index.html

check out this link, they have just about everything. I would imagine you want to go with something that is equivalent to a 480 or 540 brushed motor??