I don't understand the interest in Najera. I think Scal is the better player of the two, particularly on the defensive end and his ability to play multiple positions.
Josh Boone is a liability on the offensive end and the defensive end. He is one heck of a rebounder though .... but the C's are the best rebounding team in the league right now, there is no need to carry all those offensive/defensive problems for Boone.
Sean Williams is an interesting prospect. I'd rate him as having a low likelihood of ever fulfilling his talent though, so he's a risky prospect in my eyes. I wouldn't be willing to give up someone as valuable as Tony Allen in order to acquire Williams. If Sean were available in a Delfino type situation, say two second round picks, I'd be happy to see the C's make a move on that.
On top of the below par talent coming over in return, the club loses TA? The only wing who currently provides quality contributions. Losing him without any clear plan of who will replace him? I don't like that.
I don't see the virtue of this deal. I think this trade would make the team worse in many different ways. I wouldn't be willing to make this deal.