I just picked up our 2008 Yukon XL 2500 from getting an exhaust put in. There is a lot of great systems out there for these rigs. The one my local exhaust place carries is the Spintech system. He could get others but I have been taking my cars for exhaust and things I cannot handle myself to him for almost 10 years and he has never lead me wrong. We put in the dual out exhaust with both tips coming our straight back under the rear bumper. It was a little more than I thought about $500 total but he also fixed a busted bolt on one of the manifolds. After doing some research online and reading about the brand and how it performs I thought it would be OK. I was wrong, it was more than just ok. I sounds great, not too loud but definitely not stock. I am not a kid anymore and didn't want something that simply sounds loud, I wanted a bit of performance as well. Without an actual Dyno test I cannot tell for sure but it does definitely feel like it made a difference, especially when you punch it. Look up some videos on the Spintech units. I plan on taking some pics later today after I install the K&N intake. Good luck on your search and congrats on the new toy.