dude, stop. don't go to crutchfield.
way too expensive. that sub is only $99.99 at sonicelectronix.com
you paid double...
return it, get these subs (same thing, but single voice coil/ 2 ohm each, so combined total of 4ohm)
and run this amp (500RMS at 4ohm):
That will run 250 RMS to each sub, and they are rated to 300RMS, so they will last quite a long time, and will sound incredible. I'm only running one at 300RMS now and it's loud.
Also, custom build a box. I'm building a box and getting rid of the speaker mounts in the back, and all the other extra crap that takes up room. everything behind the seats I'm pulling and just going to make a flush, carpeted box that will house two subs, two speakers, and two amps.
Go with the setup I posted here, its great, and give's quite a kick and a good balance between rock and rap directed subwoofers.