Yep. Run both if you can.
If you are looking at the X-ray, also check out the Corally, TC5, and Tamiya stuff. I'd get a car that your hobby shop supports - otherwise you'll need to guess what parts to stock up yourself.
If you're not willing to spend the cash, your electronics should work in on-road.
13.5 is super stock
17.5 for RCGT
21.5 for Trans Am
What classes does your track run on carpet?