Not sure that will solve your desire for a wider tire and stability on gravel. I see they have a 700 x 28, is that much different from your 650B's Also confirm that fender's will fit. If you have a chance, go ride a Surly LHT to compare the ride and comfort. Of course, I will totally confess to being a steel is real rider who loves the comfort of a steel bike.
Good luck in your search!