Tires are not going to make a huge difference in ride. This isn't a Lexus. Going to 14" wheels will get you a softer tire, with a higher sidewall. However, if you want a cushier ride, I'd get new struts and bushings. Yours are probably failing. You'll want the rubber bits that seperate the strut from the tower, and new control arms with bushings/ball joints. This will tighten up the handling and make it less bouncy.
