S4 2-7T

I have decided to junk the Bose speakers/amps on my 2001.5 S4, but keep the headunit for fit/look issues.
So...
1.I want to have the Bose speakers taken out and replaced, what size do I need to get for the front component speakers? What size do I need for the 2 rear decklid speakers?
2.I am having this done at either Tweeter or Circuit City, so is there anyway you could leave specific instructions/details on what I need to have done in order to hook a 4 Channel amp to the Bose headunit? (right now I have a subwoofer and amp running off the back speakers, so please also include details to tell them in order to run that amp off the headunit instead of the back speaks)
3.finally, could you tell me what extra parts and adaptors I will need and where I should order them from to complete this install?

I know this is alot to ask, but you seem to have this info down to a science (and CC and Tweeter certainly do not, so I'd like to pass your instructions to them, so that they don't hook it up the wrong way) I would REALLY APPRECIATE it!!

Thanks!

MacSub

The fronts are 4" mids with 1" tweeters, the rears are 6.5" coaxials. You may find Bose rears are different but they will use spacers in the 6.5" holes, which can obviously be removed.
Both sets of speakers will need adapter rings to be able to mount them as Audi use a bizarre 3 point fixing. Most companies that provide these adapter rings allow you to use 5" or 5.25" mids up front. Some of the adapter rings are worse than useless and either don't fi at all or leave an airgap between the adapter and the baffle = crap sound). Best bet is to make your own, or at least check the ones they propose to use.
All you need to hook up the HU to a four channel amp is the Blaupunkt RCA adapter. This plugs into the non standard mini ISO socket on the back of the HU (yellow plug) and gives you standard RCA's and remote on for front & back.
You'll need another amp for the fronts (or sub) as the HU only has 25w on board for the front speakers only.
You'll also want to get the HU decoded for the Bose system. Audi dealer or someone with VAGCOM can do this for you.
The URL here has all the bits but are UK based, I'm sure someone on here can give you a US supplier.<ul><li><a href="http://www.caraudiodirect.co.uk/product_info.php?products_id=79">http://www.caraudiodirect.co.uk/product_info.php?products_id=79</a</li></ul>

HIS4

If they cannot figure out the basic stuff themselves then I wouldn't even bother because their just going to hack it up and when it doesn't work they'll give you a whole bunch of BS reasons why it not their fault. Go to a shop that has some experience doing what you're trying to do.

As far as what you will need, you will need to get either the blau adapter to utilize the low level outputs on the head or you will need to tap into the existing wires to extend the existing low level output from the rear deck. The rest is just hooking up speakers to the amp.