What are the differences between the various 295x2 cards? The lowest priced card sits at $650, they but seem to go as high as $1,350. Are the more expensive cards worth the price, and how do they compare against something like two GTX 970s? I've seen many benchmarks and most give the 295x2 the advantage, but I have no idea what variant they are testing.
http://pcpartpicker.com/parts/video-card/#c=169
http://pcpartpicker.com/parts/video-card/#c=169