You mentioned "octa"... that's like the 810, and that's rather expensive, isn't it... even if you could get a 510 cheap on eBay?
ATI used to make a card with 12 ports. Don't know if they still do. Once saw a pic of a "72 monitor array" to show off the graphics capabilities of W7... 6x 12 port cards. Not many mobo's even support that.
This part of your message sounds rather scary to me. If you already feel unpleasant by being on the receiving end of that mains power, how do you think that your graphics card (and the rest of your computer) will feel?
Exactly. And in this case it sounds like it is not a ground loop (which often causes the "tingling sensation"). But a real mistake in mains supply. It wouldn't surprise me if the mains cable or power adapter of one of the monitors is broken and the monitor somehow finds its mains supply through the data cables and the housing of the computer. But these things are very difficult to troubleshoot remotely.
If you're getting shocks when touching the PC chassis I recommend giving your computer to a professional to check the wiring within. Apart from that, if you're losing your video cards, you could install software that will help you monitor the temperatures of the various computer components, including your video card, as well as how (or whether) the various cooling fans within the computer are working properly. Тhe same software also gives information about the voltage of the various computer components too. I am rather paranoid about the internal temperatures of my PC, so I run that software almost all the time, and good thing that I do, because some time ago I realized that my old video card was running at 100C, which is not at all normal. It turned out its fan had stopped working.