Well put it this way its going to be far lighter than a passenger : )
The heaviest parts are the sub and box 6kg's for the sub and 4kgs for the enclosure.
Mdf I have added is only 12mm thickness so very light, 6kgs tops. My amps weigh under 10kgs. and the front pods and speakers are no heavier than 6kgs
Sub 6kgs
Sub enclosure 4kgs
Mdf in total 6kgs
2 x amps 10kgs
Pods and speakers 6kgs
Wiring 3kgs
So around 35kgs, which to be honest won't make any notificable difference to performance. I have distributed the weight evenly accross the car so it has no effect chucking it in to the corners.