I'd read this earlier today and thought I'd chime in. I've been riding since 1976. I road raced bikes before switching to cars, mostly on 125 Honda GP bike, some vintage and a couple of rides on a TZ250U.
For reference if you not familiar with GP bikes, 125 (30hp 160lbs) lap times are similar to 600cc street bike lap times and the TZ250 (235lbs about 75hp at the wheel) roughly similar lap times to 1000cc street bike. Vintage bikes while not hugely fast are great fun as they slide around like mad.
These days I ride a Beta 525RS (Fancy Italian street legal dirt race bike), I do a couple of vintage MX events on my old Yamaha and a desert race each year on a YZ125.
Play riding on a 10 horsepower 200lbs Kawi and going a 100 hp bike, obviously, is a huge jump. If you'd been riding on a 125 motocross bike (same weight but close to 40 hp) that would be different. The play bike is not without merit, mini flat tracking in a field teaches you to be comfortable sliding the front and back tires regular
Cotton brings up a good point, it's not so much the power but sport bikes tend to be short wheel base, which on track is what you want but caught off guard on the street it's an issue for newer riders. The other issue is braking, watch some videos of guys running down into hairpins, are you comfortable with the back end snaking around at 75-80 mph. These are just a couple of the reasons why most long time riders don't recommend sport bikes for new riders. 600CC bikes have become incredible but they are not as user friendly as a standard.
Another factor to consider is you're weight, I'm 140lbs with all the gear on and usually have issues with bigger bikes, not because of their power or weight but mine. The bigger sport bikes springing and damping is to stiff so they tend to slide the front end waaay early even on the street. On a the standards it's not as much an issue.
One thing that wasn't really mentioned consider a proper dual sport bike; KTM, Husky, Beta and a few others make real dirt bikes that are street legal. I mentioned earlier I have a Beta 520RS, 265lbs 50HP, proper off road suspension great brakes and 45-50 MPG on the road (I have a heavy throttle hand) You can also fit them with Super Moto wheels (sticky street tires) although be forewarned the super moto set up does tend to lend itself to holligan antics.
With all that said I would buy a cheap used bike ride it for 6 months and then start looking for what you want.............what you want will likely change after you ride for the 6 months.
My .02
Tom