theeld

I am considering buying a certified 2004 s4 with 35,000 miles and I know it has the non-bose system. I may be replacing stock amplifier I imagine and am wondering where the stock amplifier is in the car, and how difficult it would be to switch it out with an aftermarket one. I know there are 10 speakers, well maybe 9 minus the sub, so I also wonder how many channels of amplification are needed to power all the speakers like the stock system does. I will probably replace all the stock speakers as well. Can anyone give me insight on this. Also, I realize some people dont see value in upgrading car audio, but that answer is not what I search for. Thank you