I dont understand that mentality kilo, thou I do understand it is one made popular by nvidia and ATI for obvious reasons. By the time you will need the 2nd 570 two new generations of cards will be out. You stick that 2x 570 in there and you now have two outdated cards topping out and still not giving you the performance of the technologies you overlooked.
Additionally, if you "future-proof" your system with this mentality and don't end up ever getting SLI or xfire, then you have wasted some money.
I think more people need to accept that multi-card rigs are purely for those who HAVE to have those 3+ monitors at huge resolutions or someone is really obsessed with a future game like bf3 and must be certain they will get 100fps in it lol.
people please stop spewing money at these companies needlessly. and if your 2 rich to just buy one awesome card...then pm me. Perhaps we can work out a way for u to buy me a new card instead.