i have a 2000 A4 and i want to install my 12" sub and i was wondering if there is any special instructions i should know about except the radio code. thx

anybody??

If you have the regular symphony radio you will need a line level converter (if your amp doesn't have speaker level inputs). Tap into the remote turn on from the stock rear amps for your amp's remote turn on. Run power cables and such.
I have 2 12" Elemental designs subs in my 2001 A4 and highly recommend upgrading your speakers and head unit. The stock speakers kinda suck.

look in DIY section there is a write up on how to install