Suggestions for Giant Killer rca coax digital cable under $500 used

I had the AZ MC2 and it was a completely adequate digital cable, but I tried a Neotech NEVD 2001 so I could use BNC at the transport end and found it bettered the AZ in just about every way by a slim but noticeable margin.  Of course, the Neotech may have sounded better due to better plugs (Xhadow RCA  and Oyaide  BNC).  Recently, I had a custom pair of Grover Huffman Pharaoh XLR interconnects built using Oyaide Focus1 XLR plugs.  I ended up trying this as a digital cable and it's great in this application.  I currently see a Grover Huffman Pharaoh digital interconnect with RCA's on USAudiomart  for $300.  It's not exactly the same as mine but I think it's very much worth looking into.  I also had the stock Pharaoh interconnect and it was also excellent sounding; the sound was quite detailed with a black background, very focused images, with warmth and a sweetness not usually associated with this much detail, in my experience.

WOW!! What a request.

The idea the Cable will be one that is not experienced prior to purchase/parting with monies and as a used item will most likely be a non-returnable goods.

If it helps in any way, the Wire Type D.U.C.C used in a Cable, proved to be very attractive between a CDT >DAC

Townshend F-1 Fractal Digital cable is as good or better than all these expensive cables. 

Analysis Plus Digital Oval.

I use a Wireworld Starlight Gold, which I believe is silver and it sounds very nicely balanced. I know swapping cables can be fun, but if you’re looking for “giant killer” results, I think you should upgrade your dac. If you sell the Pontus and move up to the Venus, you’ll likely end up spending very close to what you would fooling around with cables.  Cables are important, but the box is more important.