Hello Tom,
Most GPU cards will work fine with Premiere whether they are listed as “supported” or not. The Supported list is merely the cards that Adobe has tested with. While out of the box, Premiere will not use cards not on the supported list, you can get around this by deleting the Adobe file that lists the supported cards.
I can’t tell you the specific name of the fine for CS6, because I deleted it so that Premiere would use my Quadro K4000 card. But look for text files in the Program Files\Adobe\Adobe Premiere Pro CS6 (or whatever version you are using) with the letters GPU in it and I think you’ll figure out which it is. Delete (or rename) it, and Premiere will use your card.
Of course, if you call Adobe with a GPU issue and you’re not using a supported card, you may not get much help. But I’ve had no problem using my “unsupported” K4000, and my K2000M in my laptop, with Adobe products.
One thing I suggest you watch out for is the noise level of the GPU card. I had tried one lower-cost card whose fans were so loud I had to do all my video editing with headphones. I eventually got rid of it because it was so loud. My Quadro K4000 card is far more powerful, and is pretty much silent.
Hope this helps!