The audio quality is mainly restricted by the size and cabinet design. You might be able to replace it with one that's a tad better but I don't know if it's worth the trouble. If it's at home, I would look into getting an external system to run that and any other stuff you have. I run my radios, computer audio and music devises all through a mixer. Then it goes to a small amp and everything goes through the same reference monitors. It seems like a lot, but you can get the components at a fairly affordable price at music stores. It will last forever and makes a huge difference in the audio quality.
If it's mobile, then I would look for a way to tie it into your car audio.
Dave
-DPD Productions - Custom Scanner, MURS, & GMRS Antennas-
http://eje.railfan.net/dpdp/