The gtx590 is a serious overkill. No no and no for many reasons.
First and foremost the reason that 590 is intended for 2560x1600 or multiple display setups which i guess you don't own.
Secondly, 2x570 will cost you less for the same performance but still being a serious overkill.
Thirdly it is very hard to find, it is bulky, it has inadequate ventilations... there are so many reasons for you not to get the 590.
If you want to spend your money, and make sure you won't notice any difference on your resolution over the single 570, go for dual 570. It is your money though and i cannot sway you if you are hell bent on bragging you got the world's fastest GPU.
My suggestion: 2x6950 or 570