I'd want a greater cushion on the amps from the MGM90 - 7XL will pull a lot....
This is rated to 8s which would be fine - is the same price and goes to 160amps...
http://www.rc-monster.com/proddetail...MM160243sHCS01
I would say that your choice of motor is slightly unmatched to your spend on ESC. Also don't know what that motor will do at 60k.
I had a 9XL magnet shatter on 4s...
Q125 - no one seems to run it on 6s for long...