I also vote for the new truck . . . and go with the dually!
I've been shopping around for a new truck the past couple of weeks, and while I don't need a dually as I have a bumper-pull trailer (a dually would be overkill for me), I feel your pain as for not having enough truck!
I've been looking at both new and used, and it seems that used trucks right now cost as much as brand new ones, so each time we look at them, the used lot is less of an interest to us, since we can get a much better loan on a new one.
My current Dodge Ram 1500 4x4 is plenty of truck for pulling around the flatlands, but when it comes to pulling up into the Rocky Mountains or crossing the Continental Divide, well, let me just say that I white-knuckle it all the way up and down the mountain passes (Wolf Creek Pass is a truck killer - remember the song?)!
It is getting old with 164,000 miles on it, so is like me in that it needs a little less pressure put on the old bones (just got home from physical therapy for an arm/muscle/shoulder issue).
And even on the flatlands, when you get that dumb@$$ that likes to pull in front of you and stop or make a right turn, you want all of the stopping power you can get!
I've had so many close calls with those knuckleheads that like to pull in front of me and stop or turn that I'm almost afraid to drive in any traffic these days . . .
Now we generally try to start and end our trips in the middle of the week so we can avoid the weekend traffic!
We have two more camping trips scheduled for this season and will probably finish out both of them with our current truck, but will most likely have a new truck for next season!