I own and have heard the DACT Stepped Volume Control, I have also heard a range of Stepped Volume Controls along with a Khozmo.
When comparing Stepped Volume Controls, it was the introduction to the different take on a design being the Slagle AVC, that was what I preferred over the others.
Today within the Hi Fi Group, I have the Korg Nutube with a Khozmo Volume Control and a Prometheus TVC as a Korg Nutube Volume Control.
The use of these devices as a Volume Control with the Nutube, surpasses their performance as a standalone control by far.
The real attraction of the Korg Nutube B1 Pre-Amp' is that it really sings with a much cheaper VC, the added luxury can be considered as a later add on, as in the cases above.
My design will have the option to have the Slagle AVC attached, but as said, I have Bespoke produced VC's for my build version.