If I were the Browns I would take a flyer on Curry, assuming the cost isn't too high. I'd give up a sixth, MAYBE a fifth for him, but that's all. It couldn't hurt to see if a change of scenery and his inclusion in an up and coming defense would help him live up to that #4 overall billing.
As for the Palmer to Miami scenario, if they do that then they are entirely deserving of another 1-15 year, even moreso if they gave Cincinatti a second or third rounder for him. He's not getting any younger and I personally don't think he's been anything but average, maybe a little above average, since he came into the league. They're better off just using Henne as a stopgap until they get into position to draft Luck or another QB.