Sounds like your room is wide enough for 7.1 . The thing I'm wondering about is how you've got your surrounds mounted presently. Are they on stands close to your listening position? How far away are your surrounds from the listening position? Is it possible for you to put in a wall to divide that room up?
As far as upgrades go, I would take the money and invest it in "Big Screen" rather than new speakers. Athena's are decent enough for HT and gaming use which is your primary use. Unless your intended interest is changing more towards music, I'd think you would get a bigger smile on your face with a big screen rather than new speakers.