[suicideneil]

Sure.

With a higher voltage, you can/have to gear down, meaning you reduce the physical load on the motor & electronics & increase the torque (at the wheels) at the same time. This is better for the truck as you are making more power (watts) from higher voltage, rather than higher current (amps). Example:

1000watts / 22.2v (6s) = 45amps
1000watts / 14.8v (4s) = 67amps

It is better for the esc and batts to make your power from higher voltage and therefore lower current draw, rather than lower voltage & higher current draw, as more current = higher temps & shorter runtimes (for a given mah capacity).

In your case, a 3s and 2s lipo of the same mah capacity and C rating (only different voltages) would be just about optimum- you would need to gear down alot with 6s lipo & a ~2300kv motor, meaning higher motor temps from being under geared.

I would suggest the Hyperion G3 packs, they are a good price and very powerful, though ultimately it depends on your budget- I would read around and see which lipos are getting good reviews.

Thats not to say that 4s lipo wouldnt work, far from it, but it depends on your ultimate goals really; 45mph is fairly fast for a ~10lb MT, so a higher voltage would yield better results & runtime.