Sub Question
 

Do you need a special adapter to hook up a sub and amp to a 98 A4 with bose system? Circuit City is telling em I need one, but I didn't think I did. I know this question might belong on the audio forum, but I figured I'd get a quicker response here. Thanks!

No you can splice the line level inputs going into the amp in the trunk....
 

its not as clean and a little more work but no adapter is required.

Should a decent installation shop know this?

Anyone know of a good car audio shop near Palo Alto?

They should know what line levels are and how to splice RCA cables into them i assume. but
 

they may not know what wire is which and where to splice at etc on each particular car, so i can't say. All i know is thats the way myself and others have done it.

You need a speaker to line level adapter or an amp with speaker level inputs.

speaker level inputs will sound horrible since it would be sending an allready amplified signal to
 

his aftermarket amp. You need to get the signal before the Bose amp distorts it.

I have done it the same way to for added bass..
 

I did remove the rear deck speakers completely though since I found I had no need for them. Sounded pretty good w/ a Soundstream amp pushing Boston Pro 10's at low cruising speeds.

true...I would never do my mids and tweeters but it doesn't make much of a difference on a sub...
 

plus the bose amp limits the amount of output to the subs so I don't think it would distort too much. Anyway if you're really into good sound you need to ditch the bose system. BTW I'm running a Zapco 350 amp and a 2002 12" polk/momo sub with a line level converter and it sounds fine.

It screwed my sub up big time and i think the reason is because the Bose amp...
 

modulates the signal strength based on volume. So if you turn the vol. down the amp throws out a little more bass to give it a full sound at low vol. levels.

If you turn up the vol. the Bose amp cuts back on the bass so it doesn't distort. This varation in signal made my aftermarket subs sound muddy at some volumes and clear at others but they never hit that hard.

I think normally speaker levels would be fine but Bose has some non-standard stuff going on.