Sad as I am, I've built a custom sub woofer that replaces the factory fit unit in the A3/S3. I purchased a Bose unit off ebay, but was disappointed that they use the same flimsy, rattlely, plastic enclosure of the standard unit. This got me thinking. So I made a replica from 12mm MDF and used an Alpine 3 way amp to drive the sub (Bose speakers) & rear speakers. The difference is impressive. So I wondered if there is a market for such an upgrade. I am going to try it out using an Alpine 6.5" component driver as well, to see if the Bose components are necessary, as getting hold of these might be an issue. Anyone interested?