Upgrading 6870 xfire vs 670/7970

[newbie1337]

Hi, i'm currently considering upgrading my current system specs are as follows;

Cpu: i5 650
Gpu: amd 6870
Ram: 8gb 1600mhz

And considering upgrading to;

Cpu: i5 3570k
motherboard: Asrock extreme 4 z77
ram:Kingston hyperx beast @ 2400mhz

But i can't decide on a graphics options, i know it would be cheaper to buy another 6870 but would it be worth getting or would i be better to just pick up a new single gpu card ?

 

[Spenty]

Get a 680.