If you intend to go with dual video cards for SLI in the future, make certain of two things.
First that you have a monitor that you can appreciate SLI on (if you have a 22" or a 24" LCD, you're going to be blowing money for no reason on SLI) and second is picking a power supply, as you requested, that will do everything you need it to do. Since you're going to be going with those power hungry 470's, and based on Newegg's power supply calculator (http://educations.newegg.com/tool/psucalc/index.html
) you'll probably want a 950 watt PSU or higher, since those video cards can really suck up the juice.
I'm still learning the Intel motherboard camp as I go, so listen to Remeniz's advice in that regard. I use an i7 at work and it's a great system.