the gpus and the brands that you mentioned all offer similar performance according to the benckmarks. any of them will be a good buy in my opinion. so it really comes down to price and your personal preferences. I love ASUS DC2 series personally, they run cool, quiet and can be overclocked substantially.
I like asus dc2 as well,,,,, having a dilemma between buying asus or msi.... if i'm buying 670 then i'll probably buy the asus one, but for 760 i'm not sure asus or msi... as for radeon 7950, no one has really commented on that yet.