What about a
Vex controller? The kit can be made to work with relays, has a nice FM radio, runs off of AAs or rechargeables (your choice), you can add in a kill switch to the back of the radio (probably a good thing for something with that much power), it can tether when you want to test radio-free, and it has plenty of room for expansion. (Autonomous programs, anyone?)
A Vex kit goes for $299, and the programming kit (which you may or may not need, depending on what you need or if your friend has one) is $99. It's not that bad a deal--you might just build a Vex robot with it, too.
