The C2 with dielectric plate is the most cost effective , and will get you some experience.
Next up, would be a dedicated circular-only BUD.
After that, this 2009 thread by Pendragon gives details on the best answer I've seen posted:
It's the wideband int feed with lnb's so you would need a receiver that can control the servo. So we will see if this new product from Manhattan comes out Manhattan-Digital: News if it does add that to the rs-1933 and your good to go.
The wideband feed gets linear and circular c-band as well as Linear ku.