I did read a review where they noticed very little difference between the standard 1Gb and 2Gb cards because
the extra 1Gb didn't increase the general performance, but I think it was different with the Toxic because of increased
I would suggest googling the reviews so you can make an informed decision.
I have the Sapphire 1GB and it works great... It gets a bit loud when I turn up the fans but that's part of the deal with the 5870 card. If you plan to run 3 or more monitors then go for the 2GB otherwise put that money towards something else.