It'* ez to add the amp and subs, but as previously stated you do need to go buy a line converter for about $20 at Wal-Mart, Circuit City, Best Buy, etc.
Your BOSE amp is mounted in the trunk against the back seat on the driver'* side. Pull the big plastic false-back out of the trunk, and you'll have easy access to all the wires you need to install the converter.
Install the converter BEFORE the BOSE amp for better sound.
From there, it'* a snap to plug in the amp and subs.
BTW, since your battery is under the back seat, it'* ez to run power to your amp in the trunk..
Check the Audio Board for lots of other things that people have done.
Y2K Midnight Blue SSEi
White Cathodes in Grille/ Blue Cathodes Under Seats