Grab a young, crazy athletic DT with the first pick. The kid benches 550, weighs 310, runs a 5.0 forty. He's not the massive hogmolly type like Vea, but he's plenty big enough, and you're just not going to find his kind of strength and athleticism later in the draft -- beyond flukes. I also really like that he'll be just 21 as a rookie, and has the pedigree as a five-star recruit coming out of high school.
Beyond Payne, I wish the Rams had two other First Rounders, cuz I want them to reload at inside AND outside linebacker. A true, wrap-up, run-stuffing inside guy, and a crazy rush-end. They don't grow on trees, either, and aren't always easy to find later.
(FA and Third Round pick for those two spots. FA for corner and O-line too)
But I think the DT is the most important right now.
Brockers, Payne and Donald equals reduced rushing totals and increased sacks. That's a monster line.