Audi S4 B6 or B7?? Sat-Nav??

[Philgreg]

Ok now you guys will no doubt think me a bit of a numpty for not knowing the difference but up until Wednesday I was driving an X5. I have subsequently chopped it in for a 55 plate S4 Saloon. I have a little knowledge of Audi's having owned four including my wifes current 06 plate TT Quattro Sport. History includes 2 A4's and an A6 Avant.
Well onto the S4. I am unsure whether my September 2005 model is a B6 or B7. What is the difference? My other issue is that the previous owner did not opt for the Sat-Nav and I am considering purchasing one for a retro-fit from an online breaker of all things VW and Audi. My local independant ICE dealer has agreed to install for a reasonable £300 and provide a warranty on the installation. The model number for the unit I am considering is 8H0035192F. Anyone able to give me some advice here?
I'd be grateful for any pointers.

[Eshrules]

morning and welcome to the forum i've copied your post to a new thread in the relevant audi section, which can be found here.