get a tamiya TA05. The E10 is CRAP. I think the tamiya porsche is limited edition.
And you won't get 40mph for less than $250. I don't know US prices, but a TA05, EZrun brushless system (8.5t motor 60A ESC) and battery, as well as the radio gear will be more than that. Plus you have to build it all. If you want RTR, an HPI sprint 2 flux is just as fast, but doesn't handle as well, nor does it cope with grit as well. The stock sprint 2 should be below budget, but not as fast as you want it.
HPI E-Firestorm - Tamiya TA05 racer (carbon chassis, 10.5 brushless etc) - LRP Blast S10 BX - Revo 2.5r truggy conversion (in progress)