I have the Shaker 1000. It was the only option that when I ordered I waffled a bit on due to the price. While overpriced, I have been extremely pleased with the option. In additon to the sub enclosure there is also a rack of 4 amplifiers mounted behind the sub enclosure.
I would order this option again in a heartbeat. I am not a metalhead but when I turn off the Shaker 1000, the remaining bass just isn't enough (
not even close for me). Also there is no rattling I am aware of when the Skaker 1000 is on in my car and volume turned up, none at all.
I guess to summarize, it is overpriced but it is well integrated with the car, makes a HUGE difference sonically, visually pleasing arrangement in trunk, and is very convienent to have it preinstalled and warrentied with the vehicle.
A modification to either the Skaker 500 or 1000 that I highly recommend is to change out the rear 5 x 7's. Replaced mine last night with a pair of Infinity Kappas and the the improvement to the high end and overall audio clarity is amazing.