even with the heavier exotek chassis, I liked the feel of the vehicle with a 540 sized motor versus a 550.

To me, the Sc10 4x4 is a bit more motor-match-to-track oriented than some other vehicles that offer more gearing range by default that I saw. So, for example if you run a large track, the Tekin 4600Kv Pro4 motor can be an excellent choice. For medium to small, the Tekin 4000Kv Pro4 motor works well too.

If you want a motor with a lot more torque for a cheap price, so far I have been really happy with my Hobbywing 4000Kv 4 Pole Motor in my Tekno. Powerwise, it feels a tad more powerful than the Pro4 HD 4300Kv motor I had, but my esc runs cooler than it did with the Pro4 HD motor. Its slightly smaller than the Pro4 HD 4300Kv motor. Didn't compare weight though but I am sure someone has.