I agree on 4s if I were to buy another motor it would be the 1900 all day. You can gear it for how ever much speed you need. And if you ever get to a monster track you can put a 5S on there. If your not running anywhere Roar though I would look into 5S for the efficiency and lower temps. Its cheaper to get another lipo than another motor, unless you find 1 for a steal. Also the more cells you go up you can even shed a few grams with your battery if you get the correct mah, like the ones I mentioned earlier.