Best cartridge to reduce hum under $400 USD

What Mofi said.
I would shield the motor. The cartridge is a good one. Shielding may take some time and effort to install but would be cheaper than spending on a new cartridge that will at best be as good as the one you've got. I suggest you get sheet of mu metal and cut it so as to fit under the platter mat. It needs to be grounded, but contact with the underlying platter would likely by itself be sufficient to do that, in that case. Otherwise, lift the platter off and see if you can affix some mu metal over the motor. Then ground the shield. You could even try just a thin sheet of ordinary copper from a hardware store.

That seems like a cheap solution, will try shielding and grounding motor. Even 50% reduction in noise would be a big deal. Thanks.

Yogiboy, assuming more weight is what's needed, your thoughts on adding weight to tone arm without changing character of the sound? I have fooled around with adding blutack to various places on a tone arm on adifferent table to reduce errant vibration and all that did was take the life out of the signal. Advantage was it sticks on its own! I suppose I would want to add weight roughly equally to both cartridge and counterweight ends? What are you suggesting I use, coins OK?

I was actually thinking that I needed a medium compliance cartridge for this medium weight arm - so adding weight for Grado seems counter to that? I think the arm weighs more like 15 grams fwiw. Again, your thoughts appreciated. I guess it doesn't hurt to try adding weight.

If you go on Ebay check out head shell weights. Technics has 3 gram weights for a couple of bucks. I would give that a try. The Sonata is a light cartridge (6 grams)so I use a weight on my SME 309. You will change the VTA when you do this so make sure that the arm you have can be adjusted for VTA.

Thanks