I hear you! It does seem like a lot to do and it definitely costs a lot!
From what I got out of reading and talking before doing is this - I think of Xpel as a barrier to protect against rock chips. (We're in Arizona and it's murder on cars!) Then CQuartz is like a super wax job. The car releases dirt and beads nicely for an easier wash. I might be able to get a similar result with a regular wax, but then I'd have to keep reapplying it. I love a clean car and am good with washing, but don't enjoy the extra time on waxing.
I wasn't lucky enough to get the whole car wrapped, but I did a full nose on both. The slickness and shine on the Audi hood, which has both, as compared to the Stingray that just has Xpel, means the Stingray will get the double shot treatment too.
When the professionals see this thread, they can set us straight. But like I said, that's just how I understand it and my experience.