The mp3 player output (either radio or mp3) is through the built in soundcard on the AN430TX. This sound card is supported by the Yamaha driver under linux and resides on the ISA bus. It is a plug and play device which meant that my software has to initialize the BIOS and setup the plug-and-play options.
Like all soundcards the final amp won't drive much, so the output is fed into a 200W graphic equalizer from Pyramid. This device is attached to the dash in the front by a custom bracket. The output is split in the trunk and also fed into a 760W Sony X-Plod in the trunk to give the bottom end some help.
The equalizer is fed into the stock speaker cables and ultimately the stock speakers. It has the bottom four bands set to full cut to provide the behaviour of a high pass filter.
The X-Plod is set up as a low pass filter, and the output of it is connected to a home built sealed subwoofer enclosure with a pair of 10 inch Dual subs.
When I initially installed the system, there was a significant level of hum being introduced somwhere in the system, I eliminated this by grounding the computer case, the equalizer case and adding a "Ground Loop Isolator" from the Shack. I think that the equalizer was the culprit as it was probably designed to be grounded, and it is attached to a plastic part of dashboard.
Needless to say, the sound is pretty good. At some point in the future I will change out the stock speakers and replace them with better ones, but that is not on the radar at the moment...