RE: horsepower of your esc and motor combo
The most I've ever seen a Flux system put out on an Eagletree is 3000w, or 4.4hp. Why anyone would want to bother working it out though is anyone's guess. The only way to really find out what your setup is putting down is to strap and Eagletree on to it and watch the recorded data back. Working it out from the manufacturers specs is about as much use as a chocolate teapot, a velinion motor is 'rated to' 75a, which means that you can run it to that (for a short time) before it melts. If it averages more than about 30a during a run i'd be really surprised.
Biggest system I've ever seen in a small scale RC is a build over on RC-Monster that used a special chassis to hold 14s lipo cells and a huge Lehner/MGM combo. Recorded 9,000w on an Eagletree Graph, or over 13hp. In a Savage.