I'd say these trade talks start and end with Colby Rasmus. Peavy is a Cy Young winner...you are not going to get a Cy Young winner for Duncan or any other crappy Cardinals player we are looking to pawn off.
It's going to take some of our top prospects, most likely Rasmus included, to lock down this deal.
Like stlmark said, Todd, Anderson and Rasmus would probably be the first names brought up. I don't mind giving up Anderson, he's sitting behind Yadier Molina and will continue to do so. It's a nice problem to have and remember Yadi is only, what? 25-26 years old?
I'm torn on this deal. I'd hate to see Rasmus go without seeing him play a single game in the bigs for the Cardinals. However, Peavy, Wainwright, Lohse, and Carpenter (when or more importantly, if he finally gets healthy) and whoever you stick in the 5th spot? That's an intimidating rotation. You would win a lot of series on that rotation alone.