Advice on first MC cartridge

I would first think about upgrading the phonostage. You would waist your money otherwise. If you want $1500 new cartridge you would want, say, $2500-$3000 new phono stage.
But frankly, if I were you I would replace the entire front end including phono and cables. You want a realy good sound and are prepared to pay for it. Then why not get it? Start with the phono and work your way up, or start with the table/arm and work your way down.

update- I put a deposit on Pete Riggles string theory arm. This will give me a couple of months to decide on a cartridge while it is being made. I am leaning toward a new Lyra Delos or a lightly used Helicon, Skala. Can't go wrong with a cartridge handmade by a Japanese master and his assistant right? Also like what i have read about the Transfiguration Phoenix. A phonostage upgrade could be in the future, but I think the Nighthawk is very good. My tt may sound modest, but it is highly tweaked with a new motor, spindle/bearing, copolymer subchassis, new pulley, lead mat, outer ring clamp, bren record weight etc.
George

I am currently using a ZYX 100 cart on an RB300. The arm is slightly modified (Cardas rewiring and bronze counterweight).

I can say the combination is very good on my Gyrodeck.

The ZYX beats all Denons I have tried on the same system, as well as a few Sumikos.

I have a Lyra Delos. I love it, and I've never heard of anyone not liking it.

I agree with the Lyra Delos. I have one on my Rega P9 - a very easy combo to listen to. The build quality of the Delos is hard to imagine until you read the specs of how it is done by hand. And, the engineering behind the design is remarkably simple - why has it taken so long for this design to come forth?