7970´s success shouldn´t be overlooked
While we discuss the relative gains of the new Tahiti series cards in percentages, we shouldn´t forget the key areas in which it excels. Namely, 7970 will be much more efficient with more raw power. Which means it will enable us to have more power at less clock rates while consuming less power and also, the other way around, to be more effective and bring more performance gain at higher clock rates. Those people that only stick to stock performance in their comparisons with the current Nvidia cards are cutting themselves short.
The 7970 is about 15-20% faster than the gtx 580, the nvidia flagship, in most relevant benchmarks. As the new AMD´s 28 nm technology is much more efficient it will mean that the 7970 will bring huge overclocking value. Why ? Because with most cards you can always theoretically push the numbers up to the max. After a certain point, there is no absolute value anymore, as the marginal performance boosts don´t weigh up the heat and power output, let alone crashes and instability that occurs. The 7970 OC in practice means, given it´s extremely high clock rates and the large amount of transistors and shaders, that you can push it to its limits without breaking a sweat and all the while gaining sweet fps, not at the expense of heat and power consumption(in relative terms).
The gtx 570 and gtx 580 had its´ 30 seconds of glory but really, they are already rather redundant given what Tahiti can do. Also, a 10-15 % advance over NVidia is not trivial in this fps point. Maxing out most new titles will keep the fps nicely above 60-70, like BF3 and others, while the older cards wouldn´t actually be able to handle the standard of 60 fps with 60 hz monitors. In most games, as I´ve mentioned, higher clock rates and more efficient architecture will ensure higher consistent fps rate in pretty much any resolution, especially on the low end of the spectrum. The gtx 580 is still a good performer but has noticeably less lowest fps in games.
Let´s see what Kepler says
Whenever it releases, I´m sure AMD will drop their prices competitively, so the 79xx will be of more value in any case.