Some thoughts in no particular order...
The KLR and F650 are more like lighter BMW GS's. The can be riden hard off road,but are happier when the pace is slower. They're even happier if you just stay on the freakin' road!
The KTM 640 ADV steps it up a notch off road w/ premium suspenders and horsepower. That big factory tank means never having to worry about getting out to far. You can fly off road, but the weight will still fight you in the tech. stuff. You wont be racing EXC's! The fairing makes getting to that trailhead sixty miles away easier. Mine vibrates like a paint mixer, I guess some are better.
Steelhead has it right w/the SXC. It needs a tank right away, stock range is 50-60 miles. People will kill for a LC4 motor with a FCR41 carb, and the 04 comes with it stock, although I understand it is real lean and needs a jet kit. The 03 I rode was geared a little short for the highway. If you can do without the fairing, it's a kick ass bike.
Stay away from GS's unless you want a street bike. I had fun whipping my 03 GS ADV down gravel roads at insane speeds, then realized I was going to destroy it and bought a KTM.
That 950 KTM is neat. A little pricey to throw on the ground a lot if you're new to off road riding. I've only had a brief off road ride on one, but if you've got fast open trails that motor would definetly be entertaining!
Good luck, Fred