Does it have to be a kit?
Admins $50 robot is easy and it's programmed in C (home page)
Great versitile MCU too
Those kits looks great, but I can't see the price so tht's kind an issue
If I had to choose one I'd take the robo-pica, since I've heard of that MCU more.
PIC's also have a big user group, so help would probably easier to come by