Well don't look for it for cheap. Go buy her 2 kicker 15" L7s and big ass amps to push them. Expect to pay around $1500 min though. Or fuck it go for 2 18" SoloX's (. If you haven't heard the above stuff don't knock it too quickly. I can find you some $50 15s if you want to be able to tell people you have "15s." Heres some 15s for ya:

http://www.thezeb.com/c-15-inch-Subwoofers-6817.htm




But if you really want to take people's breath away you gotta go for these:

http://www.thezeb.com/c-18-inch-Subwoofers-6818.htm