All,
4x4 buggy is growing, but both hector and bobby thermaled their Tekin RS ESCs running 4x4 buggy sunday with 6.5 motors. Both were geared properly. In talking with Jason and doing some research it looks like even though the RS is rated to 5.5... not in a 4x4 offroad on 2S.
Jason runs an RS Pro and I didn't realize it, but I did put my lone RS Pro in my 4x4 buggy. RS Pros are pricey even used($150) so I thought I'd post something up with some alternatives for 4x4 buggy. Below is a listing with reasonable used pricing:
LRP SXX Standard or TC Spec v1 or v2(v2 software controlable): V1 $100 V2 $125
Mamba Max Pro $80 (probably the most versitle ESC available software controlable)
Speed Passion GT2.1 Pro $90 (software programable)
Hobby wing 2.1 Pro $75 (software programable)
Novak GTB $55 (probably the most bullet proof ESC available)
Mamba Max(sensorless software programable) $50
I'm sure there are more ESCs out there that will work, just posting up some of what I know will work with 6.5 or even 5.5 motors.