need help choosing setup
 

I went out driving the villain today along side our boat and it wasnt going as fast as i hoped it would, so i want to upgrade. the jeti 600 esc, how many motors can this run? could it run 2 600 graupners 8.4v from offshoreelectrics or how about 2 700 motors? or would brushless be the better way to go, if so what would i need to run 2 brushless motors. I would like to see speeds close 30mph.