Best Sonos ZP-80 Mod?

Is a basic difference between the Empirical and Cullen mods is that in the Empirical mod the reclocker is an external unit (pace-car), where in the Cullen mod the reclocker is a board which replaces a board inside the ZP-80?

Thanks much for the information, Steve. It seems like an interesting product.

I have both a CD player and unmodified Sonos ZP-80 connected to my preamp via digital outputs. I ripped my CD's to my hard drive in FLAC format. I set up my system where I had a CD in the player, and at the same time the same CD ready to play via the Sonos system. I played both at the same time and used the preamps remote to do quick A/B comparisons. All I can say is the results were inconclusive. Sometimes I thought the music through the CD player was a bit better (voices and strings may have sounded slightly more present and less dull); other times I couldn't hear any difference at all.

Has anyone else attempted this test? If so, what conclusions have you found? If you've modified your Sonos with Empirical or Cullen mods, what differences have you found over a stock Sonos or your transport?