The Benz Ace works well with the JMW-9. I started with one a few months back with my ScoutMaster and by the time it was fully broken in, it was just awesome.
I just upgraded to the SuperScoutMaster level with the Signature arm and stepped up to the Shelter 901. It sounds great but is still breaking in.
The Benz ace cartridges are a good match for the JMW-9. I am keeping mine as a back-up.