Congrats Witch!
As for the floor plan, the family room minus the optional windows and optional fireplace would make a decent setup for a LARGE flat screen witha desktop underneath for gaming.
That way you can have your home theater and gaming room all in one.heavy curtains work as well, and darker colored room paint will all help for that.
Wiring pre-drywall is sooo nice..
Make sure you wire up based on future needs. If you are going to have a home server somewhere out of the way... you could even setup up HDMI/AV/KVM/USB cables in the walls for remoteing into it or using it as your HTPC as well.
Also might be worth dropping in some empty conduit for simple future cable runs
Monoprice has some good deals on inwall HDMI cables