Motor sizing

[asid61]

Originally Posted by mreda

what would you say would be the end goal for rpm. I was recommended previously to get a motor that would have cost me 150$ each and then I was going to have to get a motor driver as well which would have been another 100$ on top of that. This would definitely help the cost project if this ends up working out.

SPARK motor controllers should work fine.
Your rpm depends on your wheel size. A higher wheel size will require a lower rpm to go as fast as a smaller wheel with a higher rpm. A 2" diameter wheel at 500 rpm will go:
2 *pi inches/rotation * 500 rotations/minute * 1 minute/60 seconds
= 52.4 inches/second, or 4.36 feet/second (fps).
If you're not very familiar with this sort of thing, finding somebody who is experienced or simply using easier, slower motors (like the motor/controller combo you were looking at) may be a better option.
Andymark and Vex also sell premade gearbox options so you don't need to make anything.