It looks like you've done your homework pretty well.
If you insist on buying a new chipset now id recommend the 930 if you are going to go i7.
But i would REALLY recommend not doing so as intel plans to launch a new chipset soon and prices will undoubtedly fall on those p55 items.
Motherboard is good ud3r by gigabyte is a home run.
I've used coolermaster ps supplies before they are great little ps's just make sure you have enough power connectors and pins, something basic you should always check for. The cables are always a little short on cm products though especially with that case(i have the haf) it's pretty damn big. The only others i would suggest are pc power and cooling or corsair and atleast 750W.
The case is an excellent choice, i love mine, but as tioga said lian li cases are really good alternate case suggestion.
Those crossfire 4850's are on par with a 285 so you are fine in that department unless you feel like selling them for a single gpu core upgrade.
That hyper 212 seems like a good cooler, the only other ones you may consider are the Thermalright ultra 120 extreme or the prolimatech megahalem. They are throwing the best numbers for air oc atm.