[dd1 question]

Yes it does work. But alot of work on home systems. I did it when setting up the shop system at work with a self powered sub. That was fun pulling the sub out

[DD-1 and 03 vs 07 Monte Carlo SS]

Depends are you using the factory radio? And if so what loc?

[Constant Distortion on 40hz only]

Check the settings on the radio. Make sure bass boost is off. Loudness off. Eq flat, crossovers set properly, and sw level is set to 0 and try again