Whoa! Can't really go wrong with any of them, but I would keep:
Beltran, Prior, Crawford & Schilling.
It might be tough letting Sheffield go, but you'll have two stud OF anyway, and another team may find themselves having to let go a stud 3B or other position players that you can then pick up.
Edit: it also means that you have two great SPs to build your pitching staff around, and so you can focus on hitters for the first few rounds of the draft.