I don't think you should have any worries about getting something that is going to be over your head.. I have been riding street bikes for about 2 years, the past year was all track days... I figured buying a dirt bike would be a cheap / fun way to hone my skills when I cant make it to the track.. I ended up picking out a Honda CRF450R rather impulsively, but have rode it numerous times @ a really challenging ORV park here in Southern California. If you know how to ride, and have a good basic knowledge of throttle control, clutch usage.. which it sounds like you do, I think you would do just fine (I haven't killed myself yet, at least

) .. Braking on the other hand, way different!
Anyway, back to the point. If money wasn't an option I would pick up a Honda CRF450X, I don't know how the laws are in RI, but in California its ridiculously difficult to get off-road bike registered for highway use.. I for one, would love to ride my little 200+ lb. dirt bike on the street, would be a blast.