Graham and Shelter matching - and other arms/carts

When you get a component that truly lifts your system up and reveals what's going on everywhere else, you learn things about your system that you hadn't realized before. My new Io Sig has shown me that I probably need a better linestage (I posted about this in Amps/Preamps), and it's also taught me something about arm/cart matching.

Now that the Io is in the system, I am hearing an unhappy balance between my Graham 2.2 tonearm and Shelter 901 cartridge. There's a tubby bass resonance that sounds to me like the Shelter cantilever feeding back into the unipivot arm structure. The outriggers on the Graham are supposed to minimize this effect, but perhaps the match just simply isn't made in heaven.

Instead, my Ortofon RS-212 tonearm, matched with Ortofon SPU Classic GM cart, is sounding much more balanced, real and musical.

That leaves me with the question of what to do with my Graham and Shelter. I'd like to have a "modern" arm/cart combo to compare with the classic Ortofon setup (I currently have 3 arms mounted on my table). My third arm is an Origin Live modified RB250, which currently has a Denon 103R mounted on it (probably not the perfect matchup either). The Shelter doesn't sound fantastic in the Rega - it's better in the Graham.

I do like the Shelter sound a lot, so I could buy an arm that's a more appropriate match for it, a Moerch perhaps. But I'd have to sell the Graham to afford that, and I kind of want to keep a unipivot.

Any recommendations for exchanging the Shelter and Denon for carts more appropriate for the Rega and Graham, or vice-versa?