Dont go for the 770s.. closed cup means an extended bass response which although sounds like the best really isnt. Go for the 990 pros, the HD700 and 600 range are amazing too. Open back gives a better approximation of monitoring, but you should really be using headphones only for checking the sound rather than relying on the final mix. Closed cup headphones are often used in recording situations to isolate a player and prevent foldback or click track leakage.

peace out.