I have the Ram 20k sliding fifth wheel hitch and yes they are made by Curt. I had it thrown in the deal along with the Ram picture frame adapter. It is a pretty good hitch; it works well and is easy to use. The downfall to it is that it is very heavy and is difficult to remove/install into the truck. I think most hitches in this range will be heavy, however.
If I were setting out to buy a hitch I would probably go with the B&W but I had mine included in the deal on the truck after I negotiated the price so I couldn't pass it up. You may very well be able to do the same thing if buying from a Ram dealer.
As for the truck, you will be very pleased with the Cummins powered Ram. They are an awesome truck and I agree with the previous poster who said the Cummins is in a league of it's own. You will be amazed at how effortlessly the I-6 pulls and the exhaust brake works so well it is difficult to put into words. And most importantly, you can plan a long trip somewhere and not have to worry about reliability. This was my #1 requirement coming from a Ford 6.0L and it feels great!:B
Good luck and please keep us posted.