[Dragon-88]

390 Duke's motor vibrates quite a bit for a 400cc and for the price you can get a way better bike. Built in India so the quality is a little questionable.

The R3 is probably the best bang for the buck in that range and holds it's value quite well and is a blast to ride. One of the best track bikes in it's category.

Kawi's ninja 300 is another nice bike. Light and nimble and there's plenty of them on the market. Kawi is also coming out with a new Ninja 400 so I would look into that also if you're looking at the Duke since the price will be about the same. I rode on a 300 all summer and I had a blast on it.. Super easy to maneuver and brakes quickly.. Rode it to Osoyoos in a day trip and it did fine, really under powered on the hill climbs.

Honda Makes a CB300r/f depending on your style another great looking bike, but I've never tried them.

Maybe also consider the Honda CB500X, good for offroading and city cruising. Upright riding position and lots of aftermarket goodies.

BMW 310 I dont have a clue, but 1st gear motorcycle school has one. Might be worth reaching out to Lee to see if its worth it. Especially since hes a racing enthusiast so he has good knowledge on them.