1) Are there any aftermarket air cooling solutions for the GFX I have chosen. I have read on the guru 3d forums that the Arctic Cooling Accelero Xtreme for the 5970 is killing one of the DVI-ports of the card, so I guess that isn't an option.
2) Is a PSU required to be certified for crossfire for it to be used for a crossfire setup (stupid question maybe?). The one I linked above isn't and I plan on buying a second GFX some time down the road when this system can't keep up with the demands of games.
Do you really need the sound card? I have found that modern motherboards have perfectly fine onboard sound. You could save some money if you determine that you don't need it, and/or you could always add one in later if you find the onboard not up to your requirements.
At 60-64 GB, I'd suggest going with an OCZ Vertex 2 (or Agility 2), or another SandForce controller SSD. I have the 128 GB C300, so I'm not suggesting you avoid it because I don't like the brand. It's just that at smaller sizes, the non-SandForce controllers lose a lot of speed on random writes. If you want to stick with the C300, I'm sure it'll be an improvement over whatever you're running now, though.
For the HDD, you should be able to get a Samsung Spinpoint F3 or Seagate 7200.12 1 TB drive for less, which would provide better value. The SATA III on the WD drive doesn't do anything, as no current 7200 rpm drive can even saturate SATA II.
For RAM, you should go with a triple-channel kit (6 or 12 GB), rather than 2x dual-channel. The i7-930 will get better performance by using triple-channel mode, rather than being forced to single-channel.
No idea on the aftermarket cooling for a 5970.
No, a PSU is not required to be CrossFire certified. What you need to make sure of is that it has enough PCI-E connectors to power 2 of your chosen graphics card. Theoretically, SLI-ready should equal CrossFire-ready. This PSU scored 8.5 at JonnyGuru, but you could probably find something better for the money. If you're spending that much money, you might consider spending a little more on a PSU that's rated 80+ Silver or 80+ Gold.
In general though, I think the build is pretty decent, and would be fine to buy as is, if you change the 8 GB ram to 6 or 12 GB.