Well, I wouldn't run the MM because of the Neu and the fact that 6s is a bit out of it's range. The Quark doesn't like 6s even though it says it is rated for it. That would leave MGM as the only high voltage choice (for what Mike has anyway). Unfortunately, like the quark, it aint cheap. I would get
this one. It has the added benefit of a built-in switching BEC (UBEC) so no need to get an external one. So, that saves ~$35 right there. And from all reports, it runs cool. The only negative is something to do with the brake or something like that, but only happens at low speed IIRC.