Sirio is a engine to see it, probably you'll be fine too with a Rally Game engine, who are cheaper than the on-road version (this is generally on all the brands who make .21's). Their powerband will be different, and probably you'll need to tune them a little different but is a very valid combo.
If you really decided what car to get, wait a little, with the Release of the Ninja engines, Mugen should be about launching a combo of the MRX4-R and the ninja engine at a slightly lower price (well, here they done them... is to expect that your Mugen dealer will do the same).
[quote=MugenDrew;2684554]BATTERIES are for FLASH LIGHTS, gasoline is for cleanin parts, alcohol is for me to drink and well NITRO...everybody know thats for racing.[/quote] :D:D:D