Id go mardave the customer service is brilliant (but iv not used kamtec yet bit he's fairly good from the reviews of other people at the track) and we recently got 2 hot hatches (hot rods) and they came 90% built out of the box (I think the mini is the same) all that needed doing was the steering linkage, fit the wheels, motor (not included but can be got from modelsport), fit the body mounts, cut, mount and paint the shell and fit the radio.
I will happily assist with advice on motor, esc and servo to meet the spec of the class, iv attached screen shots the regs from force so you can get an idea of the requirements