Thunder Tiger pro .21 is a great engine for the money $119 at amainhobbies, blows the rg away and tunes just as easily.I have a couple RGs a C6bb (to much power for my track, way overkill), and the TTR .21 The TTr is a good compromise between the two, it runs almost like the discontinued OS RZ motor(one of the best motors ever IMHO). Good luck with whatever you choose.