TX, i'm surprised you had so much trouble. Everyone seems to have had good luck using the LC2I to pull a signal off one of the speak outputs. I have placed an order for everything I need, the LC2I will be here tomorrow, and on Wednesday the Rockford R500X1D, Kappa 120.9w "went with the 12in" and a wiring kit. I will start with a free air/IB setup first to answer the question of whether or not it will work well. If I don't like it I'll build a sealed enclosure that will mount to the bottom of the rear deck.
I'm guessing the wiring diagram is different from the Sony that is posted. If anyone knows the best wires to tap for the LC2I please let me know, I assume I will only need one pair running mono. I also assume you need to tap the outputs from the amp to get vol control?