SLI vs better cards

Depends on games. if it is a game that scales very well. the 570 would still probally win. but the 550ti sli would beat for example a single 560ti. but a single faster card is always better

GTX 550ti SLI scaling is not too strong, better off to stay with single GTX 570.

when you're running a multi monitor gaming setup, and you don't want to sacrifice too much performance at that resolution. though there are still a number of issues, most common being microstutters in some cases.

as for SLI-ing a 550Ti, i'd reckon it'll perform somewhere between a 570 and a 580.

http://www.tweaktown.com/reviews/3936/palit_geforce_gtx...

Generally when using SLI or Crossfire you see much better results when you SLI an already high-end card, if you are willing to spend the cash to crossfire a lower-end card then you might as well buy a single higher end card

As according to your question.
GTX 550ti sli > GTX 560ti also (448 core)
GTX 550ti sli < GTX 570.

Basically, it's not worth putting 2 cards in sli until they outperform top of the line cards.

Or is it that the performance increase though sli relative to the individual cards is much higher with higher end cards than it is with lower end cards?

Also, wow this is a great community. I literally joined at midnight last night and posted this a while later, and got 6 replies by the next morning. And I have yet to see a single troll/asshole on this forum.

GTX 550TI SLI

biggest waste of money next to Crossfire 7770s

You are correct sir, in most cases the higher-end GPUs scale a lot better so the performance increase is far more substantial. However every once in awhile AMD or Nvidia will release a mid-range card that scales really well in Xfire/SLI and is at a price point where it would be worth it to buy two opposed a single high end equivalent. General rule of thumb though is always to buy a high-end GPU now, and then down the road when its time to upgrade you will have the option to SLI or Crossfire