oh, you have a 3.0 b6 so you most likely have the luxury package too. you have a bose neodymium 8" sub. and you can make any subwoofer fit clean with some fiberglass. but the smaller the enclosure the worse the sub will sound

 

niice

 

do you know what is the max output of the stock bose amp? So I know how much wattage the system can handle without blowing it...

would I be able to install these?

http://www.circuitcity.com/ccd/Expan...=9#custRatings

 

Assuming the 2008 still has the driver's side storage cubby in the trunk, you can add a 10 inch subwoofer and amp. Here's a prior post with photos and instructions:

https://www.audiforums.com/m_243958/tm.htm

There are tons of other useful posts linked off the one above or easily findable via search. PM me if you need more details

Cheers

 

stock bose amp is 215 watts. but if your gona add a sub, you'd want to let that amp run your speakers and deck like its doing now, and get a seperate mono amp to power the subwoofer. and i would suggest buying subwoofers off ebay. they are dirt cheap