I think that you'll love the Novak Spread Spectrum. I have one with a 6.5t motor and it really screams and I swear on everything that I haven't seen temps on it yet over 105F using a duratrax infrared temp gun! I am only doing 5 minute heats and mains indoors but it is warm inside. I am using an 18t pinion.
I haven't really noticed a difference in power between a regular GTB and the Spread Spectrum one though. They seem alike in that aspect.