Tamiya kits are usually pretty solid. For high speed, belt drive is more suitable. The TA05 should be suitable for you, the kit also includes bearings, which will help a whole lot with high speed runs. The cyclone is also a great candidate, in my area, it's very popular to race at club events, although I have never done any speed runs to give you a better review. Do not worry about the small rocks. They have not been a problem for any of my belt driven cars, and I run on my street where construction is still taking place for new homes.
So low my body sweeps pebbles.