Either find the 2.5gb 570 or get a 6970.
vram is going to be your worst enemy over the next year mate. BF3 uses 1.4gb on my 6970, a number that doesn't even fit the 570.
I had a lovely Zalman cooled overclocked GTX 470 and I had to get rid.
With drivers now the 6970 edges out the 570 and with a reasonable overclock will stand up there with a stock 580. Best of all though you get 2gb of vram.
You're going to need it over the coming months. Note all AMD's new high end cards are 3gb. That's not for fun.