The 7970 would be a horrible investment for bitcoin mining. Not even a good upgrade for gaming if you already have a decent card. Games only run so well.
IDK about dedicated bitcoin mining, but I disagree entirely on gaming. There is no magic limit on how well games run other than your video card. CPUs stopped being a factor a few years ago. My 7970 is almost twice as fast as my 5850 with the same settings in various games. I'm still way over my 5850 with all the bells and whistles turned on. The 7970 is an absolute gaming monster. For someone like me that games and does bitcoining on my downtime the 7970 is again almost twice as fast as my 5850. I'll take it since equipment cost is not even a consideration on a gaming rig.
Sapphire is total crap. 4 cards died on me in the past month alone. One just died completely and three others had cooling fan failures. And no, they were only 73 degrees C hot...
How are fans dying from heavy use an indication of manufacturer quality?
Sapphire is like the grand daddy of all of the AMD card makers. They sell the most AMD cards in the entire world and have been making cards since the dawn of AMD time. They also have an R&D role with AMD so their knowledge is second to none. That doesn't mean they don't have defects, but my research indicates they are every bit a top tier manufacturer.