I don't have nearly as much experience as a lot of people here, but if you like the 250 and just want more power, the Ninja 500 might be an option.
It's got almost exactly twice the power of the 250, in both horsepower and torque. I can surpass any speed limit in the state in 3rd gear, but it maxes out at ~120mph in perfect conditions. Not that you can't still get very dead at 120 or slower, but you don't have to worry about accidentally bumping the throttle and hitting 160. It shares a lot of parts, or has very similar parts, with the 250. It's a little heavier, but it's still a pretty small, agile bike. It has similar ergos to the 250 as well - it's sporty looking, but you still sit pretty upright. Around here, they're quite cheap too - I was originally looking for a 250, and ended up with my 500 because it was cheaper than I could find any decent 250.
Downsides: They stopped making them in '09, so used is your only option. Very little has changed on the bike since their introduction in the late '80s (there was a styling upgrade in the '90s that also fixed a few weak spots), which means they're somewhat lacking in the tech department, but that also means they're pretty simple to work on. The Gen1 looks a lot like the PreGen if you're into that "classic" styling, and the Gen2 is typical '90s styling. Some people hate that, because it's not really "classic" or "modern", it's just that odd chunk in between. It's also got separate upper and lower fairings, with the engine fairly exposed in between - again, a lot of people don't like that look.
The banana seat gives you some room to trim it down to make it easier to reach the ground, without affecting the handling of the bike by changing the suspension (by the specs, the seat height is the same as the 250). The fork springs are pretty much worthless for any adult, but that gives you a chance to buy ones that actually match your weight instead of just tolerating the stockers (if you're that short, you might be light enough for the rear spring to be a pretty good match for you). Despite their long production run and popularity in racing, there's not much of an aftermarket for them, if you're into bolt-on farkles. However, they're also tuned quite well from the factory, so you don't really need to slap on a lot of the usual stuff that people tend to do.
http://cycle-ergo.com/ can help you get an idea of how you'll fit on bikes you're looking at too. It's no substitute for actually trying the bikes out, but it'll show if you'll be hunched way over or something.