I've never ridden an xcr in an edge, but I own an edge 800 and a gen2 xcr. The power is not comparable so a 600 would be even further away. I don't think the few pounds on the nose would be noticeable. I've always loved the idea of this combination and was close to having the right components a year ago. Unfortunately the owner of the edge found a motor to replace his blown 800 and decided not to sell.
If your looking for the arm stretching power with a decent ride I think you'll be happy.