Is is possible to create an expansion card that is a down and side firing speaker? Is there enough room to house a better driver and the required glue logic? Would it be possible to achieve mono if one speaker is inserted, and stereo if two are inserted.
If so, I would be very happy give up one or two slots when I needed better audio quality, which would not be all the time.
Design considerations might include using rubberized slide rails to eliminate vibration, if needed.