Advice on first MC cartridge

Demon 103r -- add the heavy weight balance in the rear and a few gram weight to the head, thereby changing the overall mass of the tonearm and you'll be in heaven for under $500.

I did the on an RB300 with incognito wiring...

Typo

Should be DL-S1 not DS-S1

Typo, ha! Auto complete on my iPad turned Denon into Demon. Worst part is I missed it.

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