geforce 670 vs 680 ... 670 better bang for buck?

Maybe it’s drivers fault?
I still can put my hands on 580 3GB : http://www.evga.com/products/moreInfo.asp?pn=03G-P3-1584-AR&family=GeForce%20500%20Series%20Family&sw=
it’s everywhere here in Poland. So maybe it will be good idea to grab it especially since I heard that nvidia crippled down 600 3d performance compared to 500 series.