Hi Garon,
Yeah, Gary is correct.
My full setup consists of 2 pairs of Alpine Type S 6.5" coaxials (one pair in the doors, one pair in the rear), the 2 6w0's in my homemade box powered by an Alpine MRD-M350 and an Alpine CDA-9813 with the V-Drive powering the 4 coaxials.
I beleive that the amp I used (MRD-M350) has speaker inputs as well (in addition to RCA inputs), so you could if you wanted splice the signal off a set of speakers into the amp and run the subs that way off the stock headunit. However, I dont think it will sound as clean as it will with the RCA cables, plus you will not have complete control of the Sub channel, since the sound will be dictated by what comes out of the speaker you use to get the signal from.
It can be done with the stock stereo, but its not the best way to go...
Asheesh