At that sort of money you’ll not do a lot better than a CBR 600f. Bulletproof bikes, cheap insurance and great performance. About 10k revs they’re bananas. Not Fireblade fast, but fat more maneuverable and suitable for traffic. The wheelbase on the 600f is shorter (tighter and better low speed handling) and the riding position far more comfy on the wrists. The Fireblade steers like a boat in comparison.
DRZ in Supermoto form are excellent too – and they have a host of upgrade options. Fit a wr400 carb, mod the airbox and they go like stink. There are also loads of upgrades – For example, Tag precious metal clamps, all sorts. And not as service hungry as the (albeit lighter and madder WR400/WR450’s). They’ll also not overhead in traffic like WR’s have a tendency to. GO for the ‘s’ or ‘sm’ model over the ‘e’ model, as the ‘e’ like the WRs don’t have a fan on the rads and overheat in traffic.
Most Hondas will be incredibly reliable and fun. VFR or Africa twins are good shouts. As are XRs – although they’re a mite more agricultural.
Good luck with whatever you get.