Best cartridge to reduce hum under $400 USD

I am currently running a Grado platinum reference on a stock Thorens TD150 mkII and Grado phono preamp. I like the the music it produces, but on my new Arcam - Monitor Audio - B&W based system I am noticing the hum a lot more. The hum increases as the cartridges swings towards the center of the platter, so I am assuming the unshielded cartridge is to blame.

With the b&w sub I am also now noticing more rumble, which may also indicate the cartridge is the wrong compliance? If I recall correctly, the tone arm is medium weight, something like 13 grams.

The phono stage has high and low level settings, but not sure it can effectively handle low very output MC.

Any suggestions?

kn