I wanted to point out the video above for Cory Vaughn's swings. In particular, take a look at the swings from the angle just outside the cage.
Watch the end of Vaughn's swings. He cuts his hands off. It's very apparent from the 0:58 mark through 1:18 or so. It appears to me as though he's stopping his hands early. In doing so, rather than accelerating through the ball which will give him more power to drive the thing, he's decelerating early, and sapping power.
Maybe he's just working on something in batting practice and this is some kind of bat control drill, but it sure looks odd to me.
He appears to do it in one of his swings captured in this Minor League Report from the 2013 season with Binghamton.
Vaughn popped 10 homers in 71 games in Binghamton in 2013. Were he to have played a full season, that's about 16-18 hoemrs. Maybe he's big and strong enough that he doesn't need a full extension in his swing, and he's working on other priorities. On the other hand, I think this answers a question that has nagged me (well, a little bit): can Vaughn, who is big, and strong and as John Mayo says in the embedded video "looks the part" hit for more power in games? Yup, let those hands go! Full extension and follow-through will tap into his natural strength.