I "stole" the 598's for 125 Canadian on amazon day! beige only though. I hope they can get a deal like that but I think it was a stock clearance situation : /
I have a pair of HiFiMan HE 400S and they are utterly magnificent. I can't imagine wanting to replace them with any other headphone. I have previously used the Sennheiser 600, and don't see them as superior to the HiFiman at all.
I was going to buy the 598s, but I'm going to wait and see how this pans out. These are all good suggestions, but 598s are highly regarded and in my price range.