Care to share which wires you used between the factory amp and line out?The stock woofer is really tiny and light, I doubted if you will be satisfy with the bass by upgrading the aftermarket amp. It would be much better to replace with an 8" aftermarket woofer and amp. I've installed a 10" Rockford Fosgate within the factory enclosure, although it required a little bit of modification to the factory enclosure. The 8" should be fit fine with little modification. I've used the Rockford Fosgate RF-HLC Line Out Converter between the factory amp and the Rockford Fosgate amp. Pulled the power for the remote wire from the Accessory Power fuse in the fuse panel below the steering wheel by using a 10A mini fuse tap from Autozone. The bass is so much better now, I've also replaced all the speakers to the Infinity Reference Series so I am satisfy with the whole setup.