I have/had one of those 2gig gtx560's.... Palit..... RMA-ing it today. There are no ram cooling and the heat generated on the back of the card ( power circuitry ) makes the card spit and sputter when being used hard. Not good while gaming. Upping the fan speed helped a little but sound becomes annoying after while. Running 2 of those would be a nightmare. Bad choice for a card.
Also, the "only at high res" thing........... above 1900 I find extra ram a real benefit especially when turn the settings up. You may never use the full 2gigs a card has to offer but MORE than 1gig is needed a lot of time. You should rethink your plan.