Virtually any quality graphics card will work for Lightroom, since it's a 2-D app, and by comparison, less demanding. For the resolution you want, you need a card with a minimum of 256MB, but preferably 512MB. You don't say whether you will run a dual monitor setup (which I use) or a single large, like a 30" Apple or the like. With dual monitors, you really should use two cards, not one with two ports. At the moment, I use two older 128MB xFX cards to run a 24" and a 20" monitor, without problems, though occasionally the refresh is slow because of the limited RAM.