What's a good motorcycle for an intermediate level rider?

I bought a Hyosung GT250R for a bargain on craigslist for $1,500. I've been riding it for a while, and it's a great bike, just looking to move up to a bigger bike now that I've gotten some experience riding. I was thinking about the R6, The GXR 600 or the Honda CB600. I'm still not that experienced of a rider, but was just wondering what other people think.