If you're going "Off Road" you want smaller, like the DRZ-400.
If your going on dirt/gravel roads sometimes, mostly street and highway, and one bike to do it, try a R1200GS.
If you want a cheap play bike, but need to hit the slab to get to the dirt roads cause you don't want to trailer, just kinda depends on how you feel on the highway with a light bike, or the dirt with a big bike. Hear the 650 Thumpers do well.
Alot depends on your skill, comfort level, and how many times you need to pick her up.
You should think about these questions, and then try a few options/sizes out.
I'm not into dirt riding, but I like the dirt/gravel roads as an option. I probably ride 3% off pavement. I Really enjoy my R1200GS for that. Since I don't have the skill/experience, nor a close easy place to ride off road, and I don't want to trailer a bike around. It suits my needs.
I also frequent http://www.advrider.com
. You might check them out, use the search, lots of good info there.
Hope that was some help.