I assume this is in a typical dynasty situation. That being said, are you a contender this year with the likelihood of competing for a title and Allen puts you over the top? Are you struggling to just make the playoffs and this will give you a better chance?
If he puts you over the top I would lean towards doing the deal although I would still have reservations as I think you could get better for a 1st rounder. If he doesn't put you over the top then I don't do it.