If your Cannondale was sold at a time when 8 speed cassettes were available it is likely that it has rear spacing that will work for 8+ speed rear cassettes. The best thing about Cannondale bikes of that era is that they used the same frame for their high end models as they used for the lower end versions. This made their bikes ideal for upgrades. Measure your rear dropout spacing. If it is greater than 126mm it means that your bike can be upgraded to any current standard you can afford