X-band radar is not all that different than C-band. Essentially, C-band will attenuate a bit less, but the tradeoff is that you do not have as clear definition. Since weather radar is an avoidance tool, and not a penatrating one, X-band is generally considered the better wavelength for thunderstorm avoidance.
I would personally recommend you contact Dave Gwinn and enroll in his radar course. I would not recommend you waste your time on Archie Trammel's course. Also, check this web link:
http://bluecoat.eurocontrol.fr/repor..._99_Radar.html