One thing I dont think anyone touched on were tires. If you have to run kit tires only, XXX-SCT are superior to the SC-10. I just got done putting gear in a XXX-SCT to run at our track.
If your cheap like me, you can find tons of brushless systems on this board in the For Sale section. I got a new novak Kinetic in reman package for $150. Tekin RS also a good choice for brushless. You can get a 17.5 and run it in stock and then just run it boosted as you step up.