Um...ahem. OK here goes. Im assuming this is not a troll post (I'll give you the benefit of the doubt).
Is this the first sub you've had? Is the house new? How big of a room is it if your AC is shaking?
Just a few thoughts. Im running 2 12's paired, in a 2400sf house, and although stuff rattles in every room of the house, my AC doesnt.
Treating the rattles after installing a sub is normal. It took me about 3 weeks to get everything "nailed down" for example velcro on the back of all my pictures on the first floor. Using painters tape to tape the inside of my AC/heat registers. Stuff like that.
Your system has an 8" sub. If your AC ventilation is rattling, I would call your builder.