i have seen alot of people not having very good luck with the RB concepts engines but there are alot that love them, im thinking of getting the hobby 9 myself. but i would go with an werks b5 or a jammin jpx 21, i havent ran the werks engine but i hear nothing but good things about it but i have ran the jammin engine and i love that engine it has tons of power so it might not be a good engine to start racing with.