I have an EX500 and I love it. Instead of getting a bigger bike as my second bike, I think I might just buy a NEW Ex500, as opposed to the 91 that I have now. The Handling of the new bike will be much better, smoother etc. The other nice thing about the EX500 is that parts are available cheap on Ebay because its so popular a bike.
Gas prices are going no where but up, the ex500 gets about 50mpg, and to me that's another good selling point of the bike. There's plenty of power to get me in lots of trouble quick, so I'm of the school of thought that 500 is all I need.