Personally I wouldn't use Xfire/SLI for a gaming build for a few reasons:
* Mobo costs more to support Xfire/SLI, in most cases.
* PSU requirements are greater, due to more power needed to support SLI/Xfire, so the PSU cost is more.
* GPU costs are obviously more for 2 of the similar type and also generate more heat, due to the proximity of the cards to one another.
* Complexity of SLI/Xfire isn't always beneficial in all games (drivers and such).
With that in mind (assuming you haven't purchased anything yet), I would consider:
* Keep all of your parts listed (could upgrade the CPU/HSF if you like).
* Purchase a quality 500-650w PSU for around $60-80 and save about $40-70.
* Get at least a 120-128 gb SSD for OS and some games/apps with the savings from the PSU cost.
* Then in a year or so, upgrade your GPU to the latest tech that you can afford (assuming your feeling the need to upgrade).
Already purchased everything except for the power supply plus the ssd (which I will in the very near future). Do you have any brands plus wattage in mind for this build?