Active Subwoofer without Subwoofer?

[Dracconus]

Bear with me here people, although I've been in electronics/computers for almost twenty years I've NEVER needed a "boost" in my car but I feel my mirage's bass line is "lacking" a little...

SO..that being said...

I have a subwoofer which I currently have sitting in a closet. It has an in-box crossover enclosed within the unit. It's an 8ohm Dual Voice Coil speaker and gives AMAZING bass response even on a rinky dink 25 watt line coming from a tiny VM Audio system that I bought off ebay for 25 bucks as a "new toy" for my daughters room, but she didn't use it (squirt.)

**NOTE** Found out a little more about the speaker although it won't pull up much unless you're an older audiophile***

The subwoofer is a sealed box Design Acoustics 12" Subwoofer with L/R Input, and L/R Output Crossover inside the unit.

Anyways, I'm wondering if the stock radio has a sub line, and IF NOT seeing as this sub already has an active pass filter/amplifier built into it, couldn't I simply connect it to one of the rear channels (or both as it's dual voice coil) and throw it behind the rear seat and get a decent bass response from it?

It doesn't use external power, or anything like that, it's all on-board. Just audio inputs, and outputs (dual channel) that's it.
My method of thinking tells me that if I were to hook my Rear speakers wiring into the sub it would catch the bass frequencies (as it does) then the crossover would send the remaining signal to the corresponding speaker?
Any help with this would be appreciated.
Thanks