For a motor to create 1000W at 7.2v you would need to be drawing an insane amount of amps. I highly doubt Sub-C's could ever put out enough amps to create that much power.
Consider, you need to make 1000W of power from 7.2v you will need 139A, accounting for effeciency though (lets say about 60%, after all peak power isnt going to be peak efficiency). At 60% efficiency you would need 194A. And then if you factor in the voltage drop the cells will expirence at 194A, I've got no clue what that would be, but lets say its 1.0v for the whole pack you would then need 225A. Seems a bit high to me...