Recommended a highly resolving cartridge

 "I had just today received a pristine 1st UK pressing of Led Zep Physical Graffiti"

Great choice. A pedigree UK version isn't crazy priced like a UK  Zep debut

Led Zeppelin – Led Zeppelin – Vinyl (Turquoise Lettering, LP, Album, Stereo), 1969 [r1218217] | Discogs

I'm sure Bonzo's drum thwacks on "Custard Pie" and "The Rover" were proper.

"thinking of selling the Grado and finding another cart to compliment the AT! "

Your ears like the AT presentation, so it makes sense to go up the food chain to ART1000X.

Direct Power Stereo MC Cartridge | AT-ART1000x | Audio-Technica | Audio-Technica

Lyra would be on my list as well.

Lyra Delos on a Technics 'GR.  It is a cartridge legend for a reason and I am 100% enthralled with the sound of this cartridge- detail, refinement, dynamics and bandwidth are all exceptional.  

Had an Ortofon Cadenza Blue which was very good but not as refined as the Lyra and had a smaller projected sound stage.  

Also had two AR ART9- the original and an ART9XA.  While they sounded really nice, colorful and clean they could not match the performance of the Ortofon Cadenza Blue much less the Delos.  I will never take a chance on another cartridge, the Lyra does it all.

I meant to include in my post-

while the Hagerman Trumpet get rave reviews, it's often mentioned while it punches above it's price point, its still a $1500 unit-wasn't too long ago it  was under $1K?

With the cartridge level you're at, next level phono stage fits into the equation for maxing out performance.

@tablejockey This came across my mind. I suspect that the emphasized mids from the Hagerman is making the Grado not a good match anymore. SO... I could just move on from the Grado or keep it and invest in an alternate phono stage. My hesitation is that I can't see a phono stage that will beat the Hagerman by much if at all. Generally folks that suggest moving on from the Hagerman have never listened to what it does especially with primo old tubes (and linear power supply which I've added). I'd love to hear from someone that has first hand experience of the Hagerman and a pricier option and what they consider to be a worthy step up if anything. 

As an alternative to the ART20 I've bookmarked a Hana Red or a Lyra Kleos