Just picked up three new cartridges to play on a KD 500 with Grace 707 with a Shure M75ED.

Compliance is another one of those things that seems like it should be a big deal until you actually test it out and discover its not all that important after all. Which if you go on the Origin Live website and read up on their tone arm design philosophy you will find that is pretty much their view too. 

So to answer your first question yes they are all compatible.

Also will any have the potential to be better than the Shure? Sure.

Sorry to hear your arm is such a pain. Might be something there to consider for next time. Oh well look on the bright side. By the time you've swapped em out four times you'll be so good it won't be a PITA any more.

Look up your cartridge data, here: https://www.vinylengine.com/cartridge_database.php, Your tonearm’s specs, here: https://www.vinylengine.com/tonearm_database.php?make=Grace&mdl=707&sort=2&ascdesc=ASC&search=search&eflo=&efhi=&mdlo=&mdhi=&ohlo=&ohhi=&amlo=&amhi=&cw= and get your answers, here: https://www.vinylengine.com/cartridge_resonance_evaluator.php  Good website to save, for future reference.

As far as compliance goes I have to agree with Miller here.

There are combinations on paper that should never stand a chance of working and yet sometimes they just do!

My opinion even though it may be a pita to swap carts around there is only one sure way to know......

I have run some supposedly unholy combinations that worked out ok, maybe not something I would recommend say but not the "resonance all the way to Mexico" as was suggested it would be!

Out of those 3 the Empire just may put a grin on your face imho.

Thanks for all your replies. I'm still learning. But I feel confident coming here with what might be considered inane questions and get reasoned answers. "Shure. Sure" cracked me up. I paid $100 for this tonearm BITD. I can't believe how expensive they have become.  I picked up the TT for a song w/o the Infinity Black Widow tonearm 'cause the TT was scrapped to sell the arm separately. Crazy.

Not so crazy, or at least not uncommon.

I sold my Denon 1250 cw infinity black widow to Someone who had been begging me to sell them just the tone arm and I refused.

In the end they bought it all just for the Widow.

So that tt might also have been junked or sold cheap minus its Widow.