For those of you who have the Bose sub in the rear quarter panel, I thought I'd take one apart and see just what kind of a driver is in there. I wanted to upgrade my bass and have seen all kinds of threads on the 8" subwoofers but nothing on the Bose Acoustimass enclosure. I considered replacing the driver itself. These drivers are easily identified if you look through the grill and only see a couple of bass ports and no visible sub. The bad news is it looks to be a proprietary driver. The good news is they don't sound too bad, and if yours is anything like mine, it's probably in good shape. After 13 plus years in service, mine looks to be fine; it looks like new. But...it's going into storage in favor of an MTX Thunderform enclosure, JL 10" sub, and Soundstream nano 450 watt amp. It looks like the best way to upgrade is to replace the Bose enclosure. I don't think a better driver can be found that will fit , and throwing more power at this small of a driver will probably end it's life. I understand the factory amp pushes 100 watts and that's probably all the 4 x 7 will handle.