[tigerpro357]

well it also depends on the tuning of the amp, I have a 12" Infinity with a 300 watt amp, but you would never know it from the thump my car gives. At first I had the same problem, but I decided to just try messing with the tuning of my amp. After about 10 minutes I had it dialed in, and I have since added another amp for my rear speakers, I have two more amps to put in, one for another 12" Sub, one for the front speakers. Oh BTW im still using the factory HU I hate it with a passion, but I refuse to buy a stereo thats just gonna get replaced as soon as I get everything for my carputer. I would be more than willing to draw up a diagram for wiriing purposes, or maybe even a how-to if anyone is interested.

EDIT :
I almost forgot to mention that my box is not secured in any way shape or form to the trunk, i just have it sitting in the space between the trunk and rear deck.