Skifatterking

Depends on the game. If your someone who only plays one game and that game is overwatch which literally at scales 100%. Then yes. But if you play more the 1 game that supports it very well. No, definitely not worth it.

Bad idea..
Tomorrow is the announcement of NAVI. Should wait for that - and the reaction.
 
No, because Crossfire just does not work most of the times, with most games that come out this year.
There are a couple but not many...
And that's without the Scaling Problems.

I'd also not recommend crossfire for gaming. I've tried 2 and 3 way with 580's that I got just to get a 3DMark Steam achievement, and it wasn't a good experience. It's generally better to get the single fastest card that fits your needs. 
 
Having said that, 200 for a pair of 580's sounds cheap... but I'd only seriously consider it if you were putting one each in different systems, or were doing some compute that doesn't need crossfire.

On paper, yes. 
In practice... no..
 
As was said above, just wait for Navi if you can