The second problem is that you're building a i7 gaming build without a massive budget. Gaming isn't that dependent on the CPU. There is no reason to spend that much to get the biggest CPU out there and sacrifice (yes, sacrifice) GPU performance for it. I highly recommend you consider an i5 or even an AMD system. The other problem with the i7 is that Intel is replacing their current sockets within the next 3-5 months. That means there is no upgrade path. It also means that after you drop around $1,300 for a build, it's obsolete in under half a year. It doesn't look good.
So with all that said, I'm guessing you're looking to spend about $1,300 (guessing from the parts). A better gaming build for that price would be:
Yeah I originally considered triple channel, then changed my mind. I'll probably go back to triple channel since I'm well within my budget.
Just thinking though, if gaming isn't that dependent on the CPU then why would Intel's replacing their sockets make the build obsolete? On your advice, though, I'm definitely going to consider moving down a notch.
When the time comes to upgrade, I would actually either a) be willing to dump money on a new pair of cards (let's just say my budget will change dramatically) or b) give up gaming altogether for a number of years (let's just say I won't be home for some time), so the SLI issue you mentioned, while clearly a good point, wasn't much of an issue to me. I was very attracted to the 460's since I read terrific things about their bang-for-the-buck in SLI.
It's the CPUs that become obsolete. You've also got to look longer term. Once you're dropping this kind of money on a build, it should be lasting six years with minor upgrades. By that point, you'll be needing a new CPU, which means you don't have any place to go. Of course, that's four or five years down the line.
Also, let's say that games finally advance to the point where they absolutely need quad core CPUs (we're not there yet). There will be a noticeable decline in the games you can play with a quad at that point. The reason for this is that you won't have any where to off load the extra background processes to. Right now, the majority of games need dual core CPUs, which is why a triple core is considered the minimum. So if you went with an i7 build, your only choice for an upgrade would be the i7-980, which you might not be able to find at that point. It's literally the first generation of six core CPU, meaning it's wouldn't be a good choice.
Compare that to AMD, where you'll likely have two years worth of CPUs to choose from. Instead of upgrading to a four or five year old CPU as your only choice, you'll have some good two and three year old CPUs to choose from that will also be dirt cheap.
I'm not here by any means to tell you what you should buy. I'm just giving more information. If you've got your heart set on dual 460s (which aren't bad by any stretch), you'll definitely want an Intel build. AMD doesn't natively support SLI, which can be a problem with the few AM3 boards that will allow it. I'd suggest the i5-750 (or 760) and an Asus P7P55D-E Pro in that case. Together, those will cost about $340.
I wouldn't ever worry about a machine lasting six years - even with all sorts of upgrades... Just make yourself something nice for a good price now.
I've currently got a very similar build to your proposed one - and I definitely enjoy it. Also, two 460s offer performance at high resolutions better than a much more expensive 5970, or even two 5870s. They are by far the best video card value right now.
If I were you, I would either go with the i7 930 and 6gb RAM, or else the i5 760 and 4gb. Don't worry about what processor you can put in your motherboard in 4 years. Buy a new motherboard in 4 years. Stick with the 460s, and don't worry about going to 480s ever IMO. By the time your 460s feel slow to you, there will be some sort of 660s or 760s out I bet...