+! for keep.
Unless it isn't working for you, it will be better in the long run to keep. I also have the 2006, mine with 167K miles currently. I pay almost nothing anymore for title, and insurance is negligible. It also needs work, but nothing traumatic. I will be looking at transmission, window motors, and some interior rattles which should be fixed up.
You know exactly how well the truck was maintained and what needs to be done. With a newer model, you don't. Plus i've heard that the active fuel management on those vehicles leads to issues.
The Raptor looks cool, and 450 hp / 500 lb-ft out of a V6 seems awesome, but it wont' be as nice as your Avalanche.