That's an easy one...I'd do that in a heartbeat. Palmer has never been the same since his injury and Crabtree, while has potential, is still very unproven and not on the most WR friendly offense...Brees is the best QB out there and will pretty much attempt the most passes of any QB each year. I think you do it without a doubt.
YES!!! Brees is still a young QB and the best fantasy QB in the league right now. Who knows what you're getting with Palmer and Crabtree? I'd take this in any format league. no question. Especially with the Wrs you already have.
Your getting proven goods in Brees, we know what he can and most likely will do.
Your giving up Palmer (who I like yes) but is still a bit of a risk and loses one of his best (if not thee) receiver. And Crabtree who is a rookie and the bust rate isn't anything to ignore.
And when it boils down to it, you wouldn't be starting Crabtree anytime soon (I'm guessing not sure on league settings but you have 3 top 5 WRs) so basically you are trading starting points from Palmer up to Brees.
I would do it. Your WR depth is insane. You have the chance to get the #1 fantasy QB and I would get him. You just never know with rookie WR's, Crabtree could be the next Larry Fitz, but he could also be the next Troy Williamson. Take the sure thing in Brees.