A pair of GTX580's would be nice for this setup because a GTX580 in SLI supports triple monitor. Most powerful single GPU in the market and when in SLI is way more powerful than a GTX590 by a mile. Add in a Core i7 2600K @ 4.5GHz + Z68 board and you're good. Pick a board with proper slot spacing as well, you would want at least a single slot of space between GPUs to let them intake cool air.
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