I race supermoto and I have a Honda CRF450R and I love it. If you plan on riding on the street with your tard then I would go with a KTM 625 SMC, a Husquavarna 610 SMR, or some of the bigger Husabergs. The Huskies and Husabergs will cost a pretty good amount of cash, $8-9K for a new one. You can find used KTM 625 SMCs used for $4-5K. They make pretty good road bikes, they are 6 speeds and have pretty long legs for a motard while remaining fairly light. I would stray away from the DRZ 400s if I were you because my dad has one and it's pretty doggy on power. I would have to do EXTENSIVE motor work to be happy with the power on that bike. The KTM 950 SM has good power but it's so heavy I consider it more of a street fighter than a motard. I would never jump one and would not really want to drop 3 gears at 90mph and slip the rear end out to full lock, there's just too much weight moving around, it's basically a naked sportbike.
If you plan on racing though, it's a WHOLE different ballgame. All of the above mentioned bikes suck really bad on the track and you will not even be remotely competitive. Good track bikes are: Honda CRF250 & 450, Yamaha YZF 250 & 450, Suzuki RMZ 250 & 450, Kawasaki KXF 250 & 450, KTM 450, 525, and 560 SMRs, and the expensive Huskies and Bergs. The best bang for your buck on track bikes are the KTM SMRs. They are competitive out of the box. The guy that I bought my Honda from spent $11K building it, and it's no faster than the stock $6500 KTMs.
So there are a lot of options depending on how you are going to ride. Motards are the only way to go. I have had a lot of sportbikes, but since I have started riding motards, I could care less about sportbikes. Go to the track with your buddies on their Gixxers and spank them all over the place on your 450cc bike. It's a blast! Also when you crash, you pick it up and keep rollin. No busted fairings, rearsets, clipons, all that crap. You have to trash a motard pretty good to make it unrideable.
PM me if you want to talk about any of that, I don't mind. I'm totally obsessed with motards and I can try to help you with any questions you have.