Though I have an 07 I can help a little bit on this topic.
Total Install Price was about $300
When I had my catbcak done I went with the Magnaflow 22" Polished stainless muffler with a dual walled Magnaflow tip.
I then went up to the local exhaust shop and had the guy saw off my muffler and the rear resonator which is the ugly muffler sticking out the back of 07-Up Tahoes.
He then installed the Magnaflow Muffler, added some pipe to replace the resonator and painted all the Cat-back piping black with High Temp Flat Black paint under my request.
The setup is perfect, gained a throaty sound at cold starts and a good purr at about 20-40MPH, at 60MPH the sound is still a litttle more noticable and better than stock but not loun or annoying at all, NO DRONE AT ALL.
Also got about 10HP and 10Torque, about 2MPG or about 50 more miles a tank, and the tip comes out from the rear left corner giving the truck a good look.
My pipes are 2.75 in diameter and yalls Gen Tahoes are I think 3in, but Boostaholic and JKMotorsports can verify for sure.
And Sepiroth, only the 50 series Delta from Flowmaster will give you noticable sounds gains, the other won't!