The type of ram won't matter. (GDDR)
The (XFX, PowerColor, VTX) are just company names.
XFX is usually spot on with their customer service, at least I think so. I'd look into that.
There isn't too much, if any difference from the cards. The major difference would be what the outputs would be. (VGA, HDMI, DVI)
Check out some of the different versions here, and look at the ones with the most reviews/best reviews and make your choice. But be sure to select a version with an output that your monitor/TV can connect to: