I have a friend of mine who currently is running 2 Asus GTX 670 in sli, he is looking to sell them. I however am at this time only interested in buying one of the two. I have a friend who is currently looking for a new graphics card(currently using 7870). The only deciding factor is if my friend buys one of the two, and right now he needs a bit more convincing. He currently is looking at getting a Asus r9 280x. Links down below are of the card my friend is selling first, then the second one is the r9 my friend is looking at, any help or ideas are appreciated. I personally think the 670 beats a 280x but, i cant find much as far as facts on that.
Asus GTX 670
http://www.newegg.com/Product/Product.aspx?Item=N82E16814121707
Asus R9 280X
http://www.newegg.com/Product/Product.aspx?Item=N82E16814121803