I know you can run multiple cards for multiple monitors, I'm just not sure if it would run the full power of each card per monitor. 4GB is what I'm giving him for the new build (once again, I don't know his current setup). With the budget he's given me, I really want to go with a 45nm quad cpu so then I could really overclock that thing.
It seems that using the Asus Rampage with its 2 PCI-E x16 2.0 lanes, that both video cards should be able to run at full tilt and as long as one monitor is plugged into each card, it seems to reason that each monitor would have it's dedicated video card and would therefore run games on both monitors at the same time just fine.