My thoughts/experience:
Tow Rig - '06 Duramax LB SRW w/ bags
Trail Rig - '93 Land Cruiser (~6000lbs)
Camper - 9' Palomino Maverick (~2500lbs dry/empty)
Trailer - 10k Iron Eagle (2000lbs)
On toy hauler:
Besides something custom, I couldn't find anything affordable that was rated for a ~6000lbs rig. On top of that, a super long toy hauler won't fit in some of the places I like to camp.
On extension:
I don't like them, but I'm not completely against them. The SuperHitch double beam with chains is the only thing I would consider using.
On Campers in general:
My camper is 3 season, has a bathroom, no slides, no AC. It is great for summer camping or boys wheeling trips, but family camping in foul weather sucks. It feels like we are on top of each other when all inside and not sleeping (2 adults and a 3 year old).
On truck limits:
For my SRW truck, the limiting factor is my tires. My 10ply tires are rated for ~3200lbs each (6400lbs rear axle). With a full tank and no load, my r axle weights are 4200 front / 3200 rear. With my camper I'm 5000/5000. When I hook up my trailer, I assume about 10% tongue weight (800lbs). So that leaves me with 6400 - 5000 - 800 = 800 lbs extra payload for food / water / passengers.
My AAM 11.5" axle is rated for 10klbs. With bags, my truck frame/suspension is just as strong as a DRW duramax which has a higher payload than my tire can handle.