For those that are interested I decided to go with the DFRobotShop Rover V2 - Arduino Compatible Tracked Robot (XBee Kit)
http://www.robotshop.com/dfrobotshop-rover-tracked-robot-xbee-kit-4.html
The main reasons I went with this kit: Arduino based, and expandable. Once I get it up and running I am planning on adding a raspberry pi or pandaboard to it and see how far I can push it.