I would just keep the GTX 480 and not mess with two GTX460's .you will be loseing memory ,going from 1536mb to 1g.Plus you already have the GTX 480 ,if you want faster then save up and go with two GTX 480's .But I can understand wanting some new toys to play with .It just ever once in a while SLI does'nt work with a game and then you would miss that extra power.They both will draw around the same power ,but the SLI GTX 460's will run 12c to 18c cooler and will be more Quiet.
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