Best tonerarm match for Acutex M320 III STR cartridge

I have lately been having feedback problems with using the bespoken Acutex cartridge in my Dynavector 501 arm. It sounds spectacular until the feedback sets in.Usable information on what tonearm might be a good (or bad), match is not easily found. The tonearm is mounted on my heavy plinth, with my Garrard 401 'table. It sits on a wall mount stand, Brightstar BigRock 2 sandbox, with Edensound large brass footers, that are six pounds each. 

My phono stage is a Modwright SWP 9.0, that has a resistor installed to cut low frequencies. One other factor is a 15" subwoofer that is about 10 feet away, that might be a factor.

Any information would be greatly appreciated.

Thanks, and regards,
Dan