I don't have a X but I would say that on any car, mudflaps will help protect the side from debris off your tires.
I saw a thread on the other site about someone who made their own from generic flaps at the auto store. They looked good, not too flashy. I believe they guy had a VIII or IX but I'm sure you could do the same.
I'll be making some soon since Mitsu never made flaps for ours, and the ones you can buy on the web are priced a little high.
Another good way to protect your car is with a clear bra. 3M clear vinyl. I have my whole front end, the rocker panels, side mirrors and edge of doors done. I've had my car almost 2 years now and no chips or scratches where it's protected. I've had the film/vinyl get scratched but it did not make it through to the paint. Great stuff!