Well if thats the case you may as well get started now on an RB25 and not waste your time on an RB20
As much as i LOVE RB20's 240-260rwkw is really pushing the safe boundries of a stock motor and above that will require you to build the motor but it will never have the torque an RB25 will give you.
Personally i'd stick with the RB20 but thats just me