The Purist is a wow cable. You put it in the system and you hear a big difference. Over time, though, you start to hear the weaknesses. For me, the biggest issue was the high frequencies. With copper, if you don't get it just right, there is a roughness to the top end. Its not bright, but a grainy or grit, type of sound. It was easy to hear with the PAD. The Cardas does it too, but not nearly as much. The only copper cables I've heard that completely eliminate this type of flaw are very well designed solid core cables. My AQ and Tara don't have that trait.
Another thing the Cardas did better was resolve detail. It just allowed more information to pass through it and the sound was much more balanced as a result of it.
One thing to keep in mind, though, is that every system is different. Other people may not get the same results I did. Also, my system is more detailed than most, and that will be a factor too. Looking at the rest of your system, I can say that it doesn't have the detail mine does, but enough that you should be able to pick out what I didn't like about the PAD. Unless you can demo before you buy, I would look at a different cable, or just keep what you have. The Cardas is an excellent cable.
Another thing the Cardas did better was resolve detail. It just allowed more information to pass through it and the sound was much more balanced as a result of it.
One thing to keep in mind, though, is that every system is different. Other people may not get the same results I did. Also, my system is more detailed than most, and that will be a factor too. Looking at the rest of your system, I can say that it doesn't have the detail mine does, but enough that you should be able to pick out what I didn't like about the PAD. Unless you can demo before you buy, I would look at a different cable, or just keep what you have. The Cardas is an excellent cable.