ATI HD 5850 or HD 5870

I currently have a ATI HD 4870 but am going to be building a new system over a period of a couple of months. I dunno what card to buy though, i can either get 1 HD 5850 1GB with the possability of getting a second in the future, but that comes with the risk of not being able to get hold of the same card again... or i can push the boat out and get 1 HD 5870 1GB... i have compared memory clocks and so on.. and of course the 5870 as i understand it is a hell of a lot faster then 1 5850, but comes with one hell of a price tag :-o

So what would you recommend? if i were to get 2 x 5850's that would cost me more in the long run, but wud it out perform a single 5870 or shud i just part with my cash and get a 5870?

 

In most cases a motherboard will clock a second PCI-Ex16 slot down to x4 or x8 when CrossFire is used. Thus I suggest you get the 5870 as in the long run it will perform better than 2 5850s, especially when you take into account the fact that most programs are not optimised to run on two graphics cards.

 

Why thank you for the advice ive just been looking around for the best deal on a 5870, but ive just noticed something... it says that it features PCI Express 2.1... does tht mean i have to look for a motherboard supporting that? because i was going to get this mobo
http://www.ebuyer.com/product/169532