The 0 is a very, very nice bike. The extra for the XR gets you a better (slightly lighter) frame, a few drivetrain upgrades, and a slightly nicer wheelset. Functionally, they're the same. Would I pay the difference? Yes. Would I need to? No. I would say the same for you: I think you were right to go to the 0 from the 2; 0 to XR? Not at all as clear.