I just think the C6 especially is as stout as any auto, but I agree that sticks are best with diesels. I have driven diesel pickups with both autos and sticks. I have also driven medium duty trucks with both sticks and autos. As far as semis go I have driven only roadrangers, both 10 speeds and mostly 13s. In my experience I have found that shifting your own gears is the best way to get the most out of a diesel's powerband. For ease of use I would probably say the nv4500 is the most logical choice.