just want to run a few things by you to make sure I'm not too far off base with plans for my B5 S4.
First my requirements, ipod interface, sirius, bluetooth. Nav is really not important but I figure to get the others, I'm getting Nav like it or not.
I was looking at the RNS-E or RNS-D at first. The D only because the Nav functions weren't that important and I hate the gaps and color difference on the E versus the stock interior. Now I'm pretty sold on the AVIC D3. From what I can tell, it's going to meet all my requirements and while I'm not completely happy with the "aftermarket" look, I think it's about as good as i'm going to do.
Now for more where I'm lost, just from lack of knowledge on all the new technology. I just want a good sounding system that I can crank up pretty good so I'm assuming I can get speakers to fit the stock locations, throw an amp in there somewhere and I should be good to go. I don't want to get into any custom installs. The last speakers I changed were Infinity's but that goes back to the early 90's so I still need to research what's good these days.
Now I just need to get a recommended shop close by that I can trust. If I'm off base anywhere, please feel free to yell at me. Thanks

...that all sounds good to me re: your plans. what's your budget for speakers/amps combined?

IIRC The stock speakers in your B5 S4 are the same in my A4. Front are 4" with a 1.75-ish tweeter. Rear doors are 5" in think...and the rear deack are 6.5"....both dorrs are weird mounts and....

...wait...bose or non bose? (i know youre chaning the HU but the setup is different btw the two)

Provided im right...although your HU is diff from mine...i think the speaker setup is still the same. But dont quote me, we'll wait for some of the other guru's to confirm.

The PITA about the BOSE setup is that all of the speakers are 2 ohm, and powered by an amp in the trunk. So, needless to say, if youre looking to change the HU to the AVIC (which i believe is 4ohms) then you'll have to change the speakers and rewire them.

From what i know...you CAN fit 5.25s in the front doors without much effort. You CAN fit 6.5s in the rear doors...but im sure 5.25s would be easier...
B5 FAQ has some writeups.