Just bought a '99 996. It appears to have the stock M490 audio setup with a 6x40W amp, CR-210 head unit and a pair of dash and rear speakers. The previous owner had upgraded these speakers and also fitted a bazooka unit behind the rear seats. There were no door speakers but the wires were there so I picked up a set on eBay and put them in. The guy I bought them from had an M680 amp + DSP control unit that he threw in for $25. Is there any benefit at all to swapping out the m490 amp for the m680 one? Also I've read that the M680 unit will not work unless the dsp controller is connected so will the wiring harness for the M490 setup include the connector for the dsp controller?