[all variants] multimonitor and gaming ati or nvidia?

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http://ubuntuforums.org – I need to by a new graphics card, and naturally will be running ubuntu, i want to setup 4 monitors and enjoy steam, also i want a single graphics card. the way i see it i have the option for ati eyefinity and nvidia surround, which one has the best multi monitor support and easy to work on ubuntu? (Hardware)