If you are sticking with Kawasaki's, why not a ZZR600? More comfortable than your ZXR400, sporty and obviously more power/grunt than the 400.
And cheaper than a Ninja ZX6R for insurance.
Definitely get some quotes before making up your mind. At 17 I'd imagine nearly every
sportsbike 600 or above would be high on insurance, if you can get insured on them at all. Not a problem if you are willing to pay the high amounts though I guess.
The ZZR600 was also known as the ZX6E in the American market. Review here...
ZZR600 and YZF600 Review
Personally, I wouldn't just limit myself to Kawasaki's. They make lovely bikes, but so do the others. What about a Suzuki SV650, or SV1000? How about the Suzuki GSXF750? (Yes GSXF not GSXR)...Or Honda CBR600F even? And this is only mentioning sportsbikes/sport-tourers.
Try getting various insurance quotes on various different models, and then take some test rides. At least your have some fun with test-rides and get to try out the various models around, even if you're not that interested. Keep an open mind.
