Unless all your towing is uphill, both ways, I'd leave it stock and go. For the minimum towing you state I'd load her up and go. I'd say if you need to "tune" your gas engine to get the job done, you should probably be looking at a diesel. Pick your manufacturer.
I had the V10 for towing a 8,500# camper. Flats and low hills it was relatively ok. Going down Rte 77 through W. VA, Va, and some of those hills, not quite so good. It got the job done, but as some like to say "let 'er rev", and that doesn't work for me. A V10 screaming along at 4500-5000 rpm does not make for a relaxing ride for me.
Bought new camper, twice the weight, bought different truck with a diesel, and rarely crack 3000 rpm. Most of the time that happens on a downhill. For me that low rpm towing grunt makes for a much more enjoyable ride.