Hi how are you doing.

I have recently bought an XT660X supermoto(i've posted in xtx review) and it's a blast.
The difference between the G650GS and the F800GS bikes is massive, single cylinder 50hp and parallel twin 82hpwith huge torque.
The build difference is also huge, the F800 gets proper suspension and sorted chassis but it is �2500 more!

If you are only ever going to do tarmac riding the XTX is the baby and for the money the BM's can't compete. Both the BM's are dual sport bikes and the F800 a very competent enduro, but if fun is what you are after then the Yam's the one. The BM's are much smoother running engines especially the twin 800 and they will all do 60+mpg so running costs are the same, at the end of the day it's whichever you want to see in your garage but money is money and pound for pound the XTX does it for me!

Hope that helps.

Cheers Bill