I need a new belt for my '17/154"/3'". I'd pay extra for the 571, but only if it's worth it. Anybody see any significant benefits from running the 571 over the 531? An online search shows that the 571 is rare, and it is not included in the latest accessories catalog on the Doo site. All of which leads me to believe that maybe it's not all that great and might even be discontinued. Thanks in advance for the feedback.