Limiting the discussion to cartridges I've owned and installed in my own system with my Walker turntable, the Dynavector is as far above the Helikon(normal output) in performance as the Helikon is above the Grado Reference. The most striking thing about the Dynavector is a sensation that vinyl playback is much less mechanical and that a pervasive form of distortion has been eliminated. Tonal balance is richer than a Helikon, but not as rich nor as rolled off in the treble like a Grado Ref. The Helikon has more emphasis on leading edge transients, but somehow the Dynavector delivers as much or more total detail. The Dynavector has a much bigger soundstage and wider dynamics than the Helikon. The Dynavector is exceedlingly natural and self-effacing on classical/jazz/folk, but when playing pop/rock it is "meaty, beaty, big, and bouncey." It is peerless in the bass. The question I can't answer is how compatible it would be with your tonearm (it is 14 g); it works well in arms with unusually high horizontal effective mass (the Walker, Dynavector's DV-507).
Have you considered the Nightingale cartridge/arm for your Graham?
Have you considered the Nightingale cartridge/arm for your Graham?