Yes you can upgrade others, but the money will be more with others as well. See when you upgrade Trackhawk you will be equal price-wise with others. So all in all, I would upgrade Trackhawk to make it equivalent price as others. I hope that makes sense. For some brands like Urus and Porsche it doesn't even make it close.At the same time the others can do stage 1 or 2 also. The torque should help us push harder and faster than the others.
I am wondering how much the others transfer power to the rear only disengaging the front.
Trackhawk $100k + 20K for Stage 2 or 3 = 120k
BMW X5M Comp $120k as-is = 120k
^ Which car would be faster? You can't beat Trachawk price.