I was trying to decide between the DT770 and 990, but I'm thinking if I can get the 770 for 130 bucks I might just go with that.
Check the version first. The DT770 Pro and the Premium versions supposedly sound very different, the Pro being "bass monsters" and the Premium 250 and 600 ohm being more neutral. If it's the Pro version, it's a goof price, but not an exceptional one, for a Premium, it is exceptional.
Also watch the impedance: you'll need an amp for those high impedance ones.