*Sorry if i repeat anything anyone said, it took awhile to get this together*
I personally don't like the AMD Phenom x6 series. I think its a waste... So with that in mind...
CPU: AMD Phenom II x4 955 if you can OC and 970 if not (You will prolly have to OC them anyways)
Intel i7 930 (And you can OC it)
GPU: I like your idea with the ATi Crossfire, but SLI talks better, works/scales better...
Two 470's in SLI (Its going to be hard to get something within your price range if you want to have SLI/Crossfire. 470's are about 300$ apiece, and the 5850's are right around that) 480's would be perfect but they are around 400$ apiece.
Your idea with the ATI's...
Mobo: I used to know good mobos for each modern Socket, but its been awhile so i would go to Newegg.com. Then go to Computer Hardware-Motherboards-AMD/Intel (Whatever you have chosen)-Advanced Search-Select the right socket type for your CPU-Select two PCI-e x16. Go through and find the ones that have SLI (For Nvidia) or Crossfire (ATI). Then go through reviews. Mobos are hard becuase there are many duds and people give 1/5 eggs on ones that are great. Go through each review, sort them by reviews that sort of thing .
Issues: IF you are SLI/Crossfiring get the I7. The AMD MIGHT be enough but not but much. You will have to OC in the end to get the full potential of those two very expensive cards. And the Phenom II x6's are almost identical to the x4's except it has two extra cores. Apps/Games can't use those extra cores so those just suck up energy... Also, if you OC, you will need to grab an extra heatsink...
I don't know much about iracing... But i do know that if you want to play modern games across monitors it will be EXPENSIVE. 1000$ is a slim price to pay .
If you have any more questions ill be glad to answer .
With some research, i acaully take back my recomendation to use the 470's. Use the 480's if possible. But if not, then take two 5850's. Or the thing you were talking about. Price per performace is great compared to the 470's.