OP, if you are considering Zu Omens, I'd wait for the next for the next Dirty Weekend sale (which according to Zu's website is scheduled around July 4th). You'd be better off paying $999 for a new pair that you can return within 60 days if you don't like them, instead of paying around $700 plus shipping for a used pair.
I have Omen DW's and love them. I also have Zu Superflys and Zu Defheads. The Omens can surprisingly hold their own with Zu's more expensive models and aren't as picky about amps. Spending more up the Zu line gives you more attack and resolution, but I find the Omens are just fun to listen to.