I do not see how the MMM is cheaper then the HV Pro (unless someone pre-ordered it from Mike a few months ago and got the discount).
As for the MMM/motor combo, I think castle has shown us that no one (not even them) knows when it will be readily available.
BTW, I do agree that once all of the kinks are worked out of the MMM and once the motor is released (and any possible kinks worked out) it would be a better option for anything larger then a buggy.
But if you want something now, Castle can't help you (unless you happen to have a motor sitting around that is perfect for your truggy already or several hundred dollars for a Neu.
{/End of Rant}