Update: 01-19-07
 
I ordered Ed's earphone adapter and custom earphones from Now Hear This...http://plugup.com
 
Wow!!! What difference. I ususally have to have my volume set at about 12 around town. Now I have it at 2-3!!!
 
Am getting some slight engine interference so I guess I will have to get a filter to deal with that.
 
I got the earphones because I always wear earplugs anyway. This way, I have the best of both worlds. If my earphones quit working, I still have my speakers in my helmet ready to be plugged in.
 
But, I don't know if I'll go back to speakers after the earphone experience - it's that good.

Update: 01-26-07
 
Discovered that I get even more noise when using the earphones with the Cruise Control engaged. Someone indicated on the GL1800 Riders site that purchasing an "in-line" volume control (~$10.00) would remedy this problem. See: http://www.gl1800riders.com/forums/viewtopic.php?t=32543&highlight=cruise+control+noise
 
Haven't tried this yet but if it works it will be an inexpensive fix.
 
Another more involved / permanent solution can be found here: http://www.gl1800riders.com/forums/viewtopic.php?t=38127&highlight=cruise+control+noise and involves removing the top shelter.