I have run a K60 rear with a TKC front on my 800GS and now my 1100GS for about 25k miles. Best all around combo possible in my experience. Good enough on the street, good enough on the dirt.
I've tried the TKC rear, it wears out too fast for me. Tried the Kenda Big Block and Mitas E09, both wore too quickly. For as quickly as they all wore out, I didn't feel they were any better on road (maybe even worse with the Kenda) and barely better off road.
I've convinced a number of friends to try this combo too and all of them have liked it as well as I have. No, they're not as good as Tourances, etc. on the street, but they're waaaaay better off road.
I've never tried the K60 front.