The BSW is a nice system but SOOOO expensive.
Here is what I did:
10" Shallow Mount Subwoofer: $64
http://www.amazon.com/gp/product/B0036MQWN8
10" Shallow Mount Sealed Enclosure: $40
http://www.amazon.com/gp/product/B003GSLDOA
Kenwood 8105 Amp: $125
http://www.amazon.com/Kenwood-Kac-81...ref=pd_sim_e_2
1. Remove rear window deck subs from trunk
2. Wire up amp (I rewired it using a heavier thicker gauge positive and negative cable from the trunk). Use existing source (sound) that goes to the subs already from the HK or non-HK amp.
3. Bolt up sub box and amp up under rear window deck. Identical to the BSW unit that Bill mentioned above.
4. ????
5. Success
BSW : $700
Bullfrog : $230 (give or take a few bucks for an amp kit or extra wiring if you need it)