on my 04.5 duramax factory shocks weren't up to towing and at about 1K miles installed bilstein 4600's. huge improvement in ride quality and control towing and empty, and still working well after 125K miles.
On my new 2015 duramax, first time towing 12K lbs, factory shocks showed again they are not up to the task for towing. Bilstein 4600's installed again, same results, better empty ride and ride control, huge improvement in control and ride when towing.
I've installed bilsteins on an S-10, chevy van, my mercedes e420 and mercedes SL500. again pleased with the results.
Give them a try. Not the lowest initial cost, but (a) they last (b) better damping than factory shocks. and low overall cost of ownership once life is taken into account.