I went with the Corsa for the quality stainless and the double wall tips over the DB. We went on a 1,700 mile trip towing and had no drone. Really satisfied with the system overall. Fit and finish is excellent, quality parts, and clamps. The only issue was on the install, getting the stock pipe off at the front. Ended up having to cut the factory mid pipe as the crush clamps had it stuck on there pretty good. Even tried a pipe separator tool and had no joy. But it wasn't going to be used again anyway. Too bad they didn't use the band clamps like on the 1500's. Would of been a lot easier.
One thing I want to do yet is reinstall the heat shield that was on the original muffler. It was held on by 2 thin band clamps that were not reusable. The shield seems to fit the new muffler just fine so I bought a couple of long bandclamps on Ebay to do the reinstall. Just been crappy weather. There was a tiny bit of heat in the bed on our trip so figured it couldn't hurt. Not sure what it was like stock as the system was installed when the truck was basically new. Got these ones, hope they are long enough. Bought 2 extra so can double up if need be.
Towing I found that 5th gear seemed to be the best. 6th bogged too much so holding 5th max seemed to work the truck a lot less. And that is with 4.10's. How much does your 5th wheel weigh? Did you get the 4.10's?
I contemplated getting the headers all summer but waited for the CARB cert since they do a visual inspection here, didn't want any inspection issues. Now it is a non issue since they are certified.
There was a guy on here that installed the headers on his 2500 and took a lot of pictures and did a writeup. Here is the link, post #48. Just send him a PM and he will email you the info. Real nice guy!