I'm in the market for a new graphics card solution costing around AUD$500-700. I would be installing the card(s) on a X79 motherboard, i7 3820, 16 gb 2133mhz ram, 1000W powersupply. The only graphics intense application would be for games. Otherwise word processing , web, etc.
I am willing to pay any amount in that price range. I would a solution that will be able to run all new games on high or above for the next 1.5 to 2 years.
Is Sli more reliable than crossfire or vice versa, are there any issues with either in terms of compatibility and support in games. Or is it better to use a single gpu setup.
Generally speaking you will get a more reliable experience across the board with a single GPU setup. However support from manufacturers has improved the reliability of the more recent cards in SLI/Crossfire.
I personally would recommend getting the single best card in your budget, this has benefits in that you will have a more powerful card now, then be you'll also be able to SLI/crossfire it in the future if it does become underpowered for newly released titles.
After reading a few reviews on the 660ti i would recommend the 670 as the best choice of the three you suggested, its got a better power/price ratio. the 670 chews though most things at the moment on high settings, cant vouch for 2 years down the line as we don't know exactly what is around the corner but it should be more than capable by then still.
Before AMD started putting out new drivers that drove up the performance of the radeon HD 7970 so that it could contend with the GTX 680, the Nvidia solution was the better GPU overall. However, since those driver updates, the Radeon HD 7970 puts up a better fight at lower resolutions and dominates the GTX 680 at resolutions above 1080p/1200p and will give you more performance in crossfire than the GTX 680 will in sli.
Battlefield 3 and Metro 2033 are some of the most intensive games currently available and the radeon hd 7970/GTX 680 plays through those games with flying colors, but again, you'll get more out of the radeon HD 7970 at higher resolutions. Also, keep in mind that if you do want to be able to play more graphically intensive games in the future, then the extra gb of vram memory from the radeon hd 7970 will last you longer and will make sure that if you do crossfire in the future, your GPU won't be hamstringed by its memory. Of course, you can see that both the radeon hd 7970 is usually beaten by the GTX 680 at 1200p/1080p in those benchmarks, the radeon hd 7970 runs those games fast enough that you won't need to care about that. In addition, the radeon hd 7970 will respond more readily to overclocking, so if you do intend to overclock, then this card will last you much longer overall.
Generally, single GPU set ups are more reliable than crossfire/sli, but you can always buy a single GPU, wait until the drivers become mature, and then buy another to get a boost in fps so that you do not have that many problems. However, the radeon hd 7950 crossfire will definitely beat the single GTX 680 or radeon hd 7970 Ghz Edition, but at the current moment, not many games besides Metro 2033 will be able to bring any of those solutions down to their knees (below 40fps) with only a single monitor. For now, the single GPU solutions from either will do you well and allow you get better performance than the 7950 crossfire if you add in another GPU later on. However, if you are playing with a multi-monitor set-up, then you will need the radeon hd 7950/7970/gtx 670/680 crossfire/sli to play at decent FPS settings.
Before anybody starts calling me out as an AMD fanboy, I have a GTX 670.