Price-wise, you are doing great. Take a look at TrueCar just to confirm, but it looks very good. I love my 2012 Lariat FX4 PSD SB. I can drive it around town without a problem and park at the grocery store. A long bed would be much harder to get along with in town.
The Nav system and Sync are awesome. I use them all the time. Sun roof only occasionally when it's cool and sunny. Could definitely live without it. The tailgate step is vital. I also put in a rubber bed mat, but not a bed liner. Wish I had the rapid cab heat.
If considering an F450, check taxes and registration cost. I'm not sure if there is a big jump or not, but a friend mentioned it when he was looking.
The only, and I mean only, complaint I have about my 2012 PSD is the puny stock fuel tank. I've been considering a 50 gal aftermarket tank by TransferFlow out of Chico, CA. When towing the boat to the coast, I have my fuel stops all figured out. However, with a new TT being delivered on Monday, I'm probably looking at a usable range of 200 miles. I won't be following the same known routes, as the goal is to explore the West. Also, diesel costs vary quite a bit in California, so I can fill up with cheaper fuel in inland areas, then make it back without buying the expensive stuff.
I usually top off the DEF tank at a truck stop every few months. Filling it from jugs is kind of a pain. Not a big deal, though. Enjoy!