If you haven't already checked it out, this is the place to go...
http://www.supermotojunkie.com/ For street tards I'd go with a Husky SM610, KTM 690 (if you can find one in your price range), or KTM 625. The 625's are a little buzzier than the 690s but still good bikes. I had a Husky SM 610 and it was loads of fun on the right roads. It seemed to be a little smoother than my buddies KTM Duke II but neither was unbearable. It took me a little while to get the hang of riding it fast, but once I did it felt like I was riding faster at a more comfortable pace if that makes sense. I'm looking at picking up a lightly used 690 (SMC most likely but possibly a Duke 3) if I can find one at the right price.
I don't like the Suzuki DRZ 400 SM since it's pretty gutless compared to the Husky's or KTM's. On the other hand they are bullet proof.
Good luck on whatever you choose and have fun.