For motor- You can't go wrong with a Tekin, Reedy, Orion, or Novak. I like the Ballistics because every single part is available, and the sensor wire comes out the side.
For batteries- DO NOT waste money on high C ratings, especially if you'll be running mod. Lots of people like Gens Ace, you can get a 5-6k mah 40c for $45-ish. Two should be plenty to practice and you can get away with only one for a race night.
All the money you used to spend on battery wars and motor maintenance- tires and track fees!
KO's are still great