I've almost decided!
As I said in an earlier post, I was looking for tires to be as fast roling on pavement as possible, and also good for weekend XC and Single Track!
And can't find any combination that could work better than this one.....

Or the other option could be Schwalbe Fast Fred 2.0 in back and Racing Ralph 2.25 in front.

Do you think this second option could be faster? I mean, is Fast Fred faster than Karma since Karma can be pumped up to 80 psi!?

Thanks a lot for your answers