Any of the top brands (AE, Losi, Durango, Serpent, etc...) are going to be good platforms. As far as speed goes, that's gonna be down to a lot more factors then the brand of truck you choose. If you have never raced off-road RC before you are in for a treat.

It's not as simple as putting a hot motor and battery in and going fast. I know several (well, ok a lot...) of people that are way faster than I am with them running a slower motor. Once you get on the track, straight line speed has almost nothing to do with getting around the track fast.

Stop by your local track and talk to folks. Find out what classes they run and go from there. It would suck if you invested money into a class of vehicle that they don't have a race class for.

In the beginning A slower vehicle is almost assuredly going to result in a fast race pace for you. It will let you learn throttle control and setup for the vehicle.

Hope this helps.