I don't think you will get much for either of them, especially for a position in need. Unless you find someone who has totally bought into the Harper hype for *this* year, you're looking at #4/5 type starters or someone like Jonathan Niese. I would try sending an email to every manager asking if they are willing to give up a pitcher for Harper. Take the best offer you get.
In a keeper league, however, everything changes. Too bad you're not in a keeper league on this one.