I'd say no, give it a whirl. I think the JMW9-Sig is a good arm. I went from a Dynavector Karat to an Ortofon Jubilee and found it to be a very worthwile upgrade. Would the Jubilee sound better on a Phantom? I'd sure as hell hope so for the cost difference, but as I haven't done a direct comparison of the same cart on the same table with only the arm variable changing I'm not going to comment. What I can comment on is a step up in cart revealed improvements with the JMW-9 Sig arm. Best of luck in your decision. Cheers,
Bryan
Bryan