Degan,
I'm not sure I understand what you mean about upgrading. Are you suggesting that I can take an older wheelset threaded for a freewheel, and somehow convert it into a cassette-type setup? I've never heard of that before. I know they make some 9 speed freewheels, but the quality is suspect and I've heard it can lead to problems with axel breakage. If I'm missing something let me know- it would be a lifesaver.