Hi, Rich, it sounds like you have a really nice system, and you're wise to invest in the front end.
I've owned VPI turntables for the past 15 years -- several incarnations of the HW19/SAMA and currently the Aries with the. The leap from the HW 19IV to the Aries provided a MUCH more musically involving experience, although to be fair I didn't A/B both tables with the same tonearm/cartridge combo (when I moved to the Aries I replaced my Moerch DP6/Promethean Super Green arm/cartridge with the JMW10 arm and Benz Ruby cartridge.
However, I was able to compare with Aries setup listed above with the TNT, and ultimately preferred the Aries.
You might consider finding a sympathetic analog-friendly dealer (if you don't already have one -- I KNOW how scarce they can be) who would make it relatively easy to trade up.
You've got a really fine turntable. It MIGHT make sense to replace the tonearm/cartridge. Unless you're a master at analog setup, I recommend having a professional do it -- the difference can be astounding.
I've found that a good dealer can set up and fine tune a turntable/arm/cartridge WAY better than I ever could. Not to mention speaker placement, vibration attenuation, and other subtlties.
For what it's worth, my audio adventures took a quantum leap when I decided to forego mail order for a dealer I trusted.