I think a good system is important when building a car. I'd guess the weight of everything would be under 60 lbs.
We put Rockford Fosgate mid's 2 - 6" in the kick panels, 2 - 6" in the rear deck, 2 - 8" subs in the trunk, amp in the trunk, and a double din PANASONIC CQ-VD6503 with navigation. Also have a color camera in the rear deck to see what's behind us. No rear view mirrors...