An abundance of benchmark information exists for both setups, with fairly similar platforms. I found that the difficulty in comparing was to find matching games. A lot of 5770 benchmarks were done with crisis, most 79XX benchmarks were done with crisis 2, and so on. I assure you that in instances where 2X5770s are running the same games as a 7970, the difference in performance was usually within 10%.
That said, there were a number of instances where the 7970 dominated due to SLI quirks.
I'm not saying that 2X5770's are better than a 7970. I'm simply pointing out that (for games on a system that meets SLIs's prereqs) adding a second 5770 is a viable and much cheaper option that will enable users to run res2k games in the short term.
Re: New 79XX drivers are faster now:
As are the 5770 drivers.
Is there a chart somewhere to show what asymmetric SLI setups will actually work? I know that you can combine stuff from the same generation (A8/A6 and 5770, 5750 and 5770), but can you combine a 5770 with a 6950 or 7950?
adding a second 5770 is a viable and much cheaper option
be sure no linux user care for a crossfire solution because the usability of the FGLRX is very bad in this kind of usage. and the Opensource driver do not have any support for crossfire.
in my point of view crossfire is windows only.
and another fact: the most linux users i know spend more money on hardware than windows users.
for example i know a lot windows XP-32bit users they do not have need for more than 4gb ram. but ram only cost 4€ per 1gb and linux users trent to have 16gb ram and more.
also windows users (gamers) buy an FX4170 (4,2ghz) because single threated speed
most linux users buy 8core-16core and more cores.
Linux users are completely computer addicted nerds/geeks.