I agree with guidry above.
We started towing our first 6000 pound TT with a Chevy 1500 Suburban and within 6 weeks burned out the transmission. Replaced the transmission and it never towed right again, so got rid of it.
It was right then we decided to get the biggest, baddest, most robust truck money could buy, because we realized eventually we'd be trading the camper for something bigger... eventually.
We found a used 3500 Chevy Dually log bed, crew cab (Gas version). We purchased a shell for the bed and we never looked back. Yes, it was absolutely total over kill for that 6000 pound trailer, but oh it towed nice.
Fast forward. The frame rusted and my service guy said it was just simply to dangerous towing anything any more. We traded for our a 3500 Chevy Silverado, dually, long bed Crew cab (Diesel). It also was used. But what a beat it was.
We then traded trailers and went to a 31 foot long camper, and the truck towed like it wasn't even there.
That enabled us to trade up again to a new Travel trailers, this time to 35 foot 10,000 pound trailer, which towed with that truck like it not even there.
The fiberglass body on that truck started spider cracking real bad and I was concerned someday a chunk of the body would just fall out. But the mechanics were amazing. Engine and transmission was awesome.
So we then traded again for our current truck and got it brand new. 3500 dually long bed crew cab Silverado (Diesel). We've had it now 5 years, and yep ... you guess it! We traded campers again.
We went Fifth Wheel this time, 12,500 pounds and 41 feet long. And that truck tows it like drinking a cool lemon-aid on a hot evening sitting on the front porch swing.
There's a fine line all of us have to draw, and that line is money. How much can you afford right now to plop down a hefty vehicle? But the truth of the matter is, if you bite the bullet now, it will save you in the long run.
Although, we learned the hard way, buying "used" was not the best move. Granted, the trucks were cheaper, but we also had problems which eventually forced us to get rid of them sooner than we anticipated. Buying new, we've not inherited a half-used up vehicle already. I wish we would have bought new when we got that first gasser.
So, listen to what folks are saying here when they say you can't ever get too big! We've been through it. We know the drill.