I have listened to both of them side-by-side and the Bose is clearly superior to the non-upgraded factory unit. Improved (off-board) amplification via stronger power reserves and increased driver amount were the biggest differences in sound. As far as OEM systems go, the Bose is pretty good. Radio reception isn't as good as other makes (probably due to the weak reception the integrated antennas in the windshield provide)but on 2-channel sources and with the Bose unit in 2 channel mode, it sounds pretty good. Once you start screwing around with the surround sound DSP processing things can get screwy...