I don't see a reason to own the 770/80s when you own the Pro 900s. The only strength the 770s have over the Pro 900 is soundstage. You are downgrading every other aspect of sound. I don't know anything about the AKGs.
I'd say the DT990 Pros, as the complimentary can.
Ok, until I just did a little search I thought the 990/250 we out of my price range of $249 but I keep finding them for $199 with shipping. So if we're only talking a $20 difference it sounds like thats the best deal out there!! One more question then since we switch to the 990... I do have an e11 as I stated earlier so that "should" be enough to power them right?? This will be my first can with that high of an impedance. And also when you game with them do you just use the Mix-Amp or do you rig it somehow to give it more power??
Thanks again, you guys have been a huge help..