Topic: Upgrading form Fireface 400 to Fireface800


i am a very happy owner of a Fireface 400. I would like to upgrade to a Fireface 800. My question are:

is the quality of the Fireface 800 really better than the 400?

is it possible to put the Fireface 800 under a macbook pro 15?

Is the headphone output better than the Fireface 400?