Tonyptony, the Shunyata Python Zitron XLR cable between the PW DAC and Transport lacked resolution and image placement and instrument separation was poor. I felt like I was hearing a blob of sound coming from the speakers that lacked coherence. The Zitron has a little added mid-bass warmth, but that was its only positive attribute to my ears. Of course, the Zitron digital cables might work quite well in other applications. I just didn't think it sounded good between the PW DAC & Transport.
Regarding HDMI cables, I have found that they all sound more similar than different -- I have tried Harmonic Technology, Wireworld Silver Starlight, Wireworld Platinum Starlight, and Supra. I would give a slight edge to the Wireworld Platinum Starlight, but this might have been a placebo effect, since the Platinum Starlight retails for $500. The Harmonic Technology may have been a little warmer than other HDMI cables, but differences were really miniscule. So, if your budget is limited, I would not play around with expensive HDMI cables. I got far more improvement in sound quality replacing Audio Art Power 1 power cords with Mojo Audio Enigma power cords on the DAC and Transport. The Mojo cords really had a profound effect on the quality and quantity of bass from the PW combo, without sacrificing anything at other frequencies.