that upgrade path can be sometimes tough to figure out. Used to have nearly the same HP system as the OP. You can start with the table and cart or the HP amp. You should be able to hear the improvements as make the upgrades. think there are two paths you can go. Start with a better HP amp like the quicksilver HP amp. Then go to a technics 1300 or 1200G with the cart of your choice. Instead of using the Denon cart with the Zen phono buy a decent SUT and run the Denon into the MM stage of the Zen.
Where to start upgrading?
I've got the itch to start a gradual process to upgrade my setup, but analysis paralysis is setting in...
The receiver and speakers are less important to me as 90% of my listening is through headphones in a finished attic space with less than ideal acoustics. My gut reaction was to upgrade the turntable and cartridge first and build around that "base". I've been looking in the price range of ~$5-6,000 for the turntable and cartridge, but would a turntable upgrade have a low ceiling for performance improvement based on the other components?
My current setup is:
Turntable: Pioneer PL-560
Cart: Denon DL-110
Phono stage: iFi Zen phono 3
Headphone amp: Schitt Magni
Headphones: Sennheiser HD650