I did it. Thanks to 'bigaudiofanatic' from here and the umpteen people whose posts I have been reading for a couple of weeks. Thanks to Douglas Baker for his awesome blog and Bavarian Sound Works. Most importantly thanks to the quotes by local shops of $700+ for what I have done in $150, as that was my biggest motivation.
Now moving to the pics:
The ride: 02 BMW 540i with DSP.
Subs - 2 x JBL GTi MKII 10"
Amp - Sundown SAE-1000D
Headunit - Stock
Wiring - Kicker 4GA kit I pulled from my honda.
Box - Sealed .75^3/Sub.
The trunk with stock subwoofer enclosure:
After I removed it:
Stock DSP Amp: