Yeah its possible to fit all of that stuff in a double. Use the space under your bed would be my suggestion. When I lived in Dykstra, my roommate was on the UCLA archery team, and he had a helluva lot of archery gear. You'll be surprised how much crap you can fit into a dorm room.
You probably won't be able to have your guitars out all the time, so I would bring hard cases. You could probably find a place to keep the amp out, though.