The 6.2L makes trucks rockets. In SUV form 0-60 is under 6s. I think my 6.0L is in the high 7s range for comparison which I never find underpowered. Everyone that owns the prior 6.2L loves it. I expect only more praise for the 2014 version.
Keep in mind the 6.2L is available without the max trailering package as well. If you want both, it will be even harder to find.
Nothing wrong with custom ordering to get the exact equipment you want. Transaction price should be the same as if a dealer had on on their lots with the same equipment. Car buying services like TrueCar, Costco, etc offer pretty good programs without the dealer negotiations.