Wow. This is really mind-blowing. I was just about to post a thread on this very topic when I saw this. I have had the K&K phono stage for a little over one year. For those that don't know, the K&K is nearly identical to the Art Audio Vinyl Reference (without the badge), having been designed by K&K's Kevin Carter. In original form (available as a kit or pre-built), it is as good or better than anything else I've heard up to about the $4K price level.
Another A'gon member suggested to me that I try the upgrade (only $85) since we had shared views with respect to the stage's virtues previously. I have to agree with him and with Blcube in that it is just a fantastic upgrade, and CHEAP for the benefit gained. It provides sound that is even more liquid and more realistic than before - and that's saying a lot. I will be anxious to compare it with even more expensive units (recognizing that price does not necessarily mean quality) to see how it stacks up. In any event, the K&K is a winner in every respect and most highly recommended.