Fixed the NavPlus site link. Posting on another thread got me into a little trouble with linking. Thanks Bajo for the note.

I am getting all US parts.
RNS-E US: 4B0 035 192 R
XM Module: 8E0 057 593 E

Because this is a unit for US cars, the AM/FM modulator should work just fine. Listened to it on an A6 Avant recently, and it was great. The MP3s that you load on the 2GB SD cards, can be played on it too. It reads the ID3 tag and shows the song info, if that is present. All my MP3s have that.
I know the 2006 A4 also has RNS-E, but not sure the face plate is quite identical in dimension. I know the faceplate is the dimensions for the C5 platform, but all the buttons are the same across the board.
All the wiring has been built by a third party, and should be all there, which I've purchased first. Not sure about the iPod interface, but from a friend's e-mail, it does seem that it is something that can be done. I did not purchase this because at this time I'm not sure I wish to pursue it. The unit works with the Bose amps currently in place. No other changes required.

Even with the US unit there are a couple of modifications that need to be done using the VAG tool. This I got covered, as most of you know I got the tool, and directions also found on the NavPlus.us site.

XM is a different module than what Symphony II uses. Wiring should be the same though. Simple change of modules should suffice. If you currently have an XM module for the Symphony II, such as myself, I'm hoping I can just pass that on to another C5 owner that has the car pre-wired for Sat radio. Passing on some savings obviously.

Thanks all for the input, and I'm really pumped for this modification. I have a few others already lined up, but want to savor each and every mod before I move on to the next project. Obviously the write ups also take time, as I usually take a ton of pictures, but enjoy sharing with the community the know how, such that they can use it and implement it if they so wish.
Can't wait for the rest of the items to arrive.