How much battery do I need?

I really need to get an eagletree, so that I have an idea of how much battery I need, in terms of C rating.

My whole point is that these controllers are getting expensive. It seems that, as of late, I've graduated to the ~$400 controllers. There just has to be a break someplace. I was hoping that going to 6S would allow me to run the ~$150 battery packs from places like truerc.

If anyone has any idea of what a Neu 1515/2.5d (1700kv) pulls in terms of amps in a 6S configuration in a truggy, please share the info. Maybe I should have gone with a lower kv motor.