I think you'll love the Grace. I've had several F9's over the years (sadly, none at present thanks to a burglary), though I should note never a Ruby and that might make a big difference. I also have the FR1Mk3F (and a spare NOS in the drawer) and there's a similarity — both cartridges present a 'big' sound, a sense of scale while preserving subtle tonal shadings, smoothness across the frequency spectrum, and sheer musicality. Both have lots of detail but not spotlighted or in your face. Both the F9 and the FR are legendary, and for good reason.
I've never heard the Signet so won't offer an opinion.
I've never heard the Signet so won't offer an opinion.