I just need a quick explanation of something.
I'm browsing for a new graphics card, and I see AMD Radeon 7970 or 7990 are both very good. However, when I search for them, I get a bunch of different results from different companies. Sapphire Radeon HD 7970, Gigabyte AMD Radeon HD 7970, MSI R7990-6GD5 Radeon HD 7990, etc. And there are pretty steep price gaps between them.
Does the company you get the graphics card matter or should I be looking at only specific brands?
7970 and 7990 are two very different cards. The 7970 is a mid/low-highend level enthusiast card, while the 7990 is an extremist level card. The different 'brands' are different third party manufacturers, each with their own designs for cooling and the like, which all have pros and cons, usually slight, but sometimes not.
There will be a 10-30 dollar difference between the 7970s, and perhaps more for the 7990s, given the variance in what the two cards offer.
Can't speak too much for which to get, as I've been an Nvidia purchaser for my last two graphics cards.
edit: To answer your question, each company's 7970 or 7990 will run at slightly different temps, draw different voltage, and hit slightly different FPS targets. To find out which works best for you, I would suggest looking at some benchmarks. Anandtech is a good one, and there are a few others mentioned in the OP