I can recommend the F650GS which is a twin. Though it actually has an 800cc it gets very good gas mileage (avg 4L/100km) even compared to the VStrom 650cc. And its 50 lbs lighter! I think it is very well balanced across all touring needs and though I have not done any extreme trips, I have done many 600km days with the stock seat with no pain (I just picked up a Sargent but not sure I like it better yet.)
With a touring windshield it is extremely comfortable on the highway WELL past 120km/h Lots of luggage options too.
I actually have the lowered version of the F650GS even though I am 6'4"...and it still fits me very comfortably!
The only thing I don't like about the bike is that it is too much fun and thus a real drain on productivity ;-)
That 800cc engine will knock insurance up a lot with a lot of companies.
I think the Versys and V-Strom are both super ugly but to each his own.