Nissan went to great lengths to balance the Z, adding (I'm guessing at the weight of the MDF board) 1/2 to 3/4 of a sheet of 3/4 inch MDF board would be at least 60 lbs. the stealth box is 10 lbs of fiberglass in the rear of the car.
I find many people replacing the Intakes an Exhaust at what some people would call expensive to help the cars performance,why would you worry about money if you can drop 50lbs of weight.
Don't forget the box has speakers in it for the $900 price tag I haven't broke the cost down for the box itself,but don't forget there are high end JL components in the box as well as the speakers.
If you have a choice between premium 91 octane and 94 octane would you complain about the cost or get the gas that would help the cars performance ?
Money isn't an issue for me I was more interested in not adding to weight in the rear of the car, that's why I was searching for the 8th speaker to remove it,an happily someone let me know where it was