MGM 16 cell models or higher. The quark 125b can do 14-16 cells or 5s lipo; 6s lipo can sometimes be abit 'twitchy' by all accounts. Lutach has some new escs that can do what you want, but he is having issues with one of them right now, so it may be a while before we see them for sale.
Mike sells the MGMs, or you can go direct to them:
http://mgm-compro.com/index.php?tid=...ics-for-models