Just read some of these comments and had a thought that didn't come across clearly in my original post, where I recommended that you get yourself a new bike.
The reason I said that was because you stated you are maxing out your cadence with the current gearing (but didn't really say under what conditions). While you could build a wheel set with higher gearing, I am concerned that your bike frame and geometry might not be so stable at higher speeds (again, you provided very little specific information for us) and may be unsafe at higher speeds.
A good hybrid bike with multiple gear rings up front and 8-11 speeds in the rear will give you a very wide range of gear selections on a bike designed to handle those speeds.
Safety is key here as is spending your money wisely. I hope that clears things up as to why I suggested a new bike, or used....