I have been looking to buy a new graphics card and the one I was looking at went on sale. The issue is, the same one is also more expensive but then has a different clock speed but with the same description and picture. Only difference is an "O" in the title. How can I tell what is what? How does clock speed even differ in what I thought was the same device? Here are the links of the 2 cards in question. Any and all information is welcome. Thank you.