I have used the spektrum system,and now currently use the nomadio sensor.IMO,the spektrum system,DX3 or DX2 are more for bashing than anything.Simply due to the fact that all the features that they lack.The servo's that they come with are ok,but for the type of racing your gonna be doing,save yourself some money in the long run and just buy some quality servos now.I can recommend the airtronics 94358 and the jr 9000s,these are both very good servos.Another problem I have found with the spektrum system is the receivers,the antenna wires have a habit of coming unsoldered in the receiver,2 of the 3 I had did this.
A nomadio system,react or sensor is a much better system,IMO.The nomadio systems,have way more features than the spektrum,not just bells and whisles.Things like expo's,servo speeds,idle up,40 model memory,and is also fully updateable through usb connection.And to top it off real time telemetry built in to the system,no other receiver is needed,or screen.That is just a small amount of what nomadio offers.Also the nomadio systems are faster and smoother than the spektrum systems.
Looks like you've spent some money on a good chassis setup/engine,why cut yourself short with your electronics?