I believe the TM starterboxes have 550 motors. If your current box has 2 standard 540 motors you can get som 21 or 23 turns rebuildable (V2) motors, much power and less maintenance, I also have 23 turns motors.

I hope one day a manufacturer will show up with an electronic box to mount brushless motors in a starterbox.

Regarding motors... If anything is alowed, get an OS 18TZ