I bet that a helluva lot of F800's spend their time sitting all farkled up in a Starbuck's parking lot with some clever little Ewan and Charlie stickers on them.
The F650 is capable off road and a lot more capable than some people imagine.
Here are a pair at about 14,000ft. Let's see some pics of an F800 at that elevation on that terrain, past a tree line.
Dirt roads, high elevations, no pansy 9-11 or park rangers telling you what you can or cannot do, it's Mexico and all in a day's riding. The F650 is capable enough.
Your only limits will likely be your tires, your ass on the stock seat, your frame of mind, and maybe the amount of oxygen. LOL!