SSSammy, here's my feedback and suggestions.
* CPU - very nice, a 3 GHz quad core yeah! But, it's quite expensive. You could get a dual core for less money as few games take advantage of 4 cores yet.
* Memory - no good. This DDR2 memory will not fit in your DDR3 motherboard. Something has to change.
* HDD - Seagate Barracuda is quiet, reliable, inexpensive, but not fast.
* Video - 4870x2 is a lot of GPU power! Never heard of Palit, so Gigabyte or Asus. What does the Asus provide for that extra $100?
* Mobo - So expensive, I wonder why? If you want DDR2 memory, this DDR3 board is not for you. Also, why 3 PCI-E x16 slots? You expect to add more than 4 GPUs? Not many people need a 5- or 6-way CrossFireX config!
* Optical - I recommend that you get a SATA instead of a PATA. There is plenty of bandwidth on the SATA bus, and the price should be similar.
* OS - sure you get 4 GB of memory, but you have to deal with finding signed drivers for everything. They are hard to find and less mature. You could install the 32-bit now and go to 64-bit later. Downside, only ~3.2 GB of memory; upside, easier to find drivers, better performance and compatibility.
* Case - Antec Nine Hundred, excellent choice.
PSU - always at least 500W of clean power, 80% efficiency or better. 80plus certification a plus (heh, heh). Check with ATI for the PSU they recommend to drive that x2 GPU.
CPU Cooler - if you are not overclocking, the stock Intel cooler is good enough as long as the case fans are configured correctly. For overclocking, I'm liking the looks of the Scythe Ninja series. The Zalman CNPS is just too darn big to me.