We've replaced and upgraded many SC430 stereo systems over the years. The best solution on the market currently is the Alpine INA-W900. The headunit is packed with all the features you need to make your SC sound great. Your main decision will be how extensive of an upgrade you are looking for. Some of our clients just opt to replace the blown speakers (if there are any) and just integrate the new DVD headunit into the factory system. Headunit installation should be handled by an experienced audio shop as a decent level of customization will be required. When we perform a headunit installation on the SC430 we make a custom kit/bezel for the new Alpine headunit to fit in the stock location. We maintain full operation of the motorized door during this process. Most importantly though is that the circuit board from the factory headunit is removed and maintained. If not, some vehicles lose total function of the navigation and climate control functions. An experienced shop should be able to install a new headunit for you and maintain operation of all interior electronics including the factory subwoofer. If you are looking for a total system upgrade then I suggest replacing all the speakers and factory amplifier with high quality components. Hope this helps a little.