My S70 has 8 speakers, no amp, and a blown rear speaker. I went to a reputlable audio place to go over options. It seemed complicated to me. The amps I was being shown here 5 channel and large in size, and for the rear speakers I was told a free-air sub could be used. It all seemed kind of complicated. <p>What is involved with just buying the standard Volvo amp and replacing the rear deck speakers with OEM ones? Can I still buy the parts needed? Would aftermarket sound better?