A great tonearm with an average cartridge will outperform an average tonearm with a great cartridge all day long.
This is spot-on advice. Listening to a great cartridge on a average arm you may never hear all the cartridge can deliver. And you might be surprised at just how good a mid-price cartridge will sound on a better arm. And yes, you may need a little more money to get there.
I've not lived with an Origin Encounter arm so I don't know how easily it lets you adjust SRA/VTA, azimuth, VTF, and anti-skate. The higher-up the cartridge chain you go the more critical it becomes to optimize cartridge setup in order to get all you're paying for. One criteria of a good tonearm is that it accomodates fine grained adjustment and you are comfortable using it. Do you feel you're getting the most from your Benz M2? If you are not satisfied that it is set up near perfect, try to get it there.
I'd ask other owners of your same table what arms they are using. You might also ask someone (a dealer?) who has a better arm and/or table to install your cartridge in his system to hear the difference that upgrades in those areas can make with the M2. You might be surprised its a better cartridge than you think.