Iam getting the same thing done on my car tommorow. My friend he would use a convertor for the AMP.
The other day, I was in the Parking lot and some guy turned his system on, Damn the bass was so loud the alarms on the parked cars went off. I dont want my car to be like that and I like the way the Stock 6CD HU looks so I decided to do it this way.

The way he is gonna hook it up is there will be no bass from the speakers and only the Sub will throw the Bass. there will be a seperate bass control with the switch.
I will post some pictures and details once its done.