I have a Suzuki DRZ 400 as my dual sport. Its a 2013 and I found it locally 2 years ago for only $3500 with 1600 miles. I wouldnt want anything smaller if you are going to do any road riding. Even mine is screaming over 60 or so, though I did go 1 tooth smaller in the front and I'm running full DOT knobbies.
It gets over 50mpg on the road, and probably around 40 in the trails.
But, its fantastic in the woods. I dont ride fast on trails, mostly just exploring. I havent found anywhere it cant go yet. Thats taking into account my intermediate skills also-lol. And since I often ride alone, I try not to get into a situation I cant get out of myself.
I believe the KLX and DRZ is the same bike in similar sizes. I know the old KLX400 was the same as mine. Not sure about the smaller models. Hondas are great also, but getting pricey. Recently rode with a guy on a Honda CRF450 steet legal model. Nice bike, 6 speed with FI, but not 3 times as nice as mine-lol.