Basic amp kit.
You just need power, ground, and to tap the OE sub for signal. Some models also need a remote turn-on too, but many now have an auto-on feature. Since the battery is in the trunk, it probably takes 15mins to wire it up. More if a first timer, but still very easy.
Originally Posted by DontHait
Pioneer TS-W261D4 or Kicker 40CWD104.
Both are DVC and can be wired to 2ohm or 8ohm impedance. If you're keeping your Audi amp, the Base amp needs a 2ohm sub and the B&O needs an 8ohm. The Pioneer is the most popular option. It is better suited for free-air and make better use of the limited stock amps power, but its also a really deep sub that protrudes into the trunk a lot. If you have the non-B&O amp, I'd recommend the Pioneer. However if you have B&O I'd go with the Kicker. While its not as efficient, the more powerful B&O amp more than makes up for it, plus its a good inch or so shallower.
There are plenty of threads in the B8 forum discussing this swap and other considerations, such as deadening the deck, using a MDF spacer ring, etc. Like I said, its a much more involved install.
Originally Posted by Sofreshs5