Pace-Car 2 between transport and DAC?

Anyone using a Pace-Car 2 between CD transport and DAC? Improvement in sound? Worth the price? What cables are you using? Thanks!
PS: Can anyone explain purpose of the optional clocks?
I have the Pace-Car 2 tuned to an Airport Express feeding into the DAC section of my Audio Aero Capitol. I stream wirelessly from my IMac to the Airport Express (AE). I'm using the Van Den Hul Opticoupler between the AE and the Pace-Car 2, and a Purist Aqeous rca digital to connect the Pace Car to the DAC. The sound is quite good... approx. 90% of what I get playing CD's in my Audio Aero CDP.

I can't speak to your question of the optional clocks as I am not that technical when it comes to computer electronics.

Let me know if you are interested in purchasing mine (approx. 8 months old), as I still find myself using my recently retubed and repaired Audio Aero CDP and just bought an INCREDIBLE tuner... a Magnum Dynalab MD-108.
There's a new version with an upgraded look. It's not on the website, but I saw a pic at S'