Hi Tony and Stef, Welcome and congrats on the new Reflection.
You do not mention enough specifics about the Ram you are looking at to give a firm answer. Gas/Diesel, what trim package... yep it all matters. The max payload is GVWR - Base vehicle weight. Your payload would be reduced by passenger weight, the weight of anything else you are putting in the truck, cargo, purses, bottle of water, etc, etc. You did not ask for my opinion.... but when it comes to a safe tow I like to have a decent amount of excess capacity and not be down to counting the lbs that are added to the truck. Will a 2014 2500 equipped properly pull your trailer yes... will it be at the top end of pin weight maybe... depending on the config. A gas 2500 6.4 hemi has more payload capacity than the diesel as the engine and transmission are a great deal lighter. If you think your reflection is the largest 5th wheel you will ever pull... you can probably get by with the 2500 in either diesel or gas.... some configurations are a great deal closer than others. I would personally recommend heading towards a bigger truck to hedge against many things.... too much crap loaded in the truck... or the nose of the trailer causing more pin weight. Maybe you enjoy your Reflection so much you would like a bigger rig..... now you have to swap trucks again.. and that is expensive. Just things to think about.
I had a very similar truck to you.... 2008 GMC 4x4 CCSB Duramax/Ally and I bought a 2014 Ram 3500 with the absolute highest towing capacity I could buy a couple of months ago (well I could have gotten a slightly higher tow capapcity with a lesser trim package, 4x2, and a reg cab.... but I "needed" this stuff)... it has more than enough capacity to tow anything I can ever dream of buying with capacity to spare. I will not have to worry about running up against any limits if I decide to stuff a bunch of firewood in the bed.... etc etc. Frankly for the safety of my family who will be riding with me, one less thing to worry about, and potential for premature wear on an expensive TV that is pushing up against limits I would consider looking at the bigger truck.
FYI... you can buy a very nice 3500 DRW Crew Cab with the High Output Cummins/Aisin Transmission, Laramie, 4x4, 5th wheel prep, rear bed (cargo) cam, 8.4AN, 4.10's, HO alternator, aux switches, and some other goodies for below $55k. You will get towing capacity of 28,900lbs with allowable pin weigh nearing 6k.
Here is the official Ram 2500 towing capacity sheet.
http://www.ramtrucks.com/assets/towi...wing.Specs.pdf
Best of luck on your decision and congrats again on the trailer.