You're way off on the trade value. Like you said, Quinn is an "unknown." His trade value is nowhere as high as you think.
Personally, I feel that Quinn will be the better overall QB. Phil Savage gave spent a 2nd and 1st to draft him, so that should tell you how he feels about him. As DA is coming off a Pro Bowl season, his trade value is as high as it's going to be. I'd trade him for the draft picks and continue building a solid team around Quinn.