I just replaced the speakers and the Nokia subs with some Rockfords and the sound is great. Replacing the 2 inch mid range from the front doors were a pita but they really don’t need to be changed. It doesn’t sound better than if you rewired a whole new system with signal processors and powerful amps but the sound output is tremendous. It sounds better than my bang and olufson system in my A4 greatly. The total cost was less than $300 but I did get a great deal on the hertz deici components. Just my $0.02Other than keeping it all original for resale, I think the DSP system is outdated and easily outperformed by current technology. It is kind of a pain in the *** to remove and rewire but it’s worth it 20 times over. The biggest issues are getting power for an aftermarket head unit and running rca/antennae cable to it from the rear. Not rocket science and doable with the wealth of info here. If you’re considering ditching it I highly recommend it!