Balls.....

The design of the bearing should have input on your intended changes. Is the ball the wear point being the softer or a thrust plate meant to wear and wear at a reduced pace not an excellerated one. Something the designer thought of before the owner ignores it.
Why not just replace the ball with one of the same material but tighter tolerances....and better lubrication. Everytime you remove the ball to either replace it or reinstall the same one you introduce a new point of contact. 
So ,  just what are you so sure you are hearing....

Thanks melm. The TNT would appear to be an apples to apples comparison as I believe the bearings are quite similar. Wondering if the sapphire thrust plate is a sapphire watch face? Thanks m.c. I was hoping you would weigh in. Are you selling one of your turntables? There is one listed with the m.c. handle in the description. The gentleman in n.j. That is upgrading the bearings has an ad on that auction site. He also has a web page under vas but it does not list the bearing mods. 

That gentleman in N.J. has the same address as VPI! It must be VPI that does the bearing upgrade!

I replaced the stock ball bearing for a ceramic (Si3N4/Silicon Nitride) on my HW-19 MkIV using the stock thrust plate years ago. Made a significant difference by being more open/transparent, tighter bass. Just as important with that was the type of oil used and the amount. I ended up using 4 drops of Motul dbl ester/5w40/4T. This was after trying several types of oil/grease.

He is referring to Steve at VAS, he also does business through ebay  as VAS, he retips, rebuilds and builds cartridges as well as the bearing replacements. I have used him a few times and am very satisfied with his work. Enjoy the music