So, I am looking to upgrade an old Grace G-840 arm.

While not a bad arm, I know there are better. The gimbal bearing is a bit clunky by today's standards.
The arms I am considering are:
An Audiomods kit for about $650.

An Advanced Analog linear tracking arm for about $600, plus about $100 for a pump. A bit more to DIY a surge tank.

A The Wand, by a New Zealand company, Design and Build. The 12" version for $630.

The Audiomods will have the most tracking error, being a 9" arm.
The Advanced Analog will have the least. But is the most finicky. And then there is the $240 silicon damping trough, which makes a big improvement, but can be added later.
The Wand has almost zero tracking error, but is pretty bare bones. No cuing lever. And it is a uni-pivot, which I have never owned, but there are uni-picot supporters, and detractors.
I get the feeling it is a great arm.
There is also the Jelco, which can be had for about $600 for a 12". But it seems the most clunky and old fashion of the bunch.
Any other suggestions and views would be appreciated.