When building the PC for the first time, just use one graphics card, then install your drivers and make sure everything is working properly before you add the second. This makes it easier to troubleshoot if there are problems when you build the rig. After adding the second card, enable sli in the nvidia control panel and you should be good to go.
edit: For your ssd, definitley get something that at least has 120GB. Some good brands would be intel 520 series of drives, crucial m4's, corsair and ocz vertex are also decent.
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