It seems to me that this is a little bit more expensive than going 2700K. The main difference being the price in boards. You can start with a very cheap SB board, and go all the way to almost as expensive as the top end SB-E boards.
It would seem to me that you should choose the board that you're happy with, between SB-E and SB and if you don't feel you're paying over the odds for a SB-E board then the 3820 is the one to go for.
Having said that I think in the vast majority of cases the 2700K wins it.
Why? Because the features on motherboards now, in my opinion, are not worth it.
Extra PCI-E lanes are only useful for the minority that run multiple graphics cards, and even then the extra lanes don't deliver cost effective performance - although if you're going for high end then you're already happy to sacrifice bang for buck.
The build in sound I've never found to be as good as a proper discrete card. Which makes me say who is going to drop hundreds on a motherboard (and likely change it in 2-3 years tops) but not prepared to drop money on a decent sound card?
USB slots... needed? Really? Isn't a couple of USB 3 ports enough? The USB 2 ports can be expanded with dirt cheap hubs.
Overclocking? First of all the higher end boards provide more stable power, usually, but other than that there's not a great deal of difference, you're going to maybe get 100 mhz more, or 200 tops... is that worth dropping an extra couple of hundred on? And it seems that board designers across the market have one basic design and they add/remove built in features to it, that would seem to indicate that overclocking performance isn't going to be greatly different across the ranges.
Memory advantages? Really? Anyone who's looked into it knows that with a discrete graphics card memory speeds don't make much of a difference at all... certainly it's the worst area to spend extra money on a build.
So.. if you can justify a SB-E motherboard then go for it.. but I seem to be seeing right through the high end motherboards so I think the 2700K is the right one for now.
Personally I'm holding off to Ivy Bridge and I'll possibly grab the top end CPU there and a dirt cheap cougar point board to pair it up with. I now suspect I'll have no regrets.