OK, since this is a dedicated GAMING machine, the clear choice is going to be an AMD CPU based system, using one of the Phenom IIs.
I know that the Intel guys are going to claim that the i7 out performs the Phenom II, and they are right, IF you are doing Video encoding, and some other multi threaded applications. For GAMING however, the Phenom IIs perform just as well as the i7s. Especially in HIGH RESOLUTION/High Quality gaming. Here is a page of a review of the Phenom II 955 that whows high resolution performance for various processors:
http://www.techspot.com/review/162-amd- ... age11.html
I would suggest that you go with an all AMD/ATI system.
CPU: Any Phenom II from the X4 920 up will be very good for IL2.
Motherboard: One with an AMD 780 or 790 chipset. I really like the ASRock boards. They are high quality and low cost. You will need to be careful in matching the MB with the CPU, as there are two different sockets for the Phenom IIs. AM2+, and AM3. Generally the AM2+ uses DDR2 memory, and the AM3 DDR3. IF you go with the X4 920 or 940, then an AM2+ will work well, and DDR2 memory is cheaper than DDR2, which with the AMD CPUs performs just as well as DDR3. If you go with the 945, 955, or 965, then you will need an AM3 board and DDR3 memory.
Video: An ATI 4870, or 4890. Either has more than enough performance for IL2. Pick the one that fits in your budget better.
One other option would be to drop down to the Phenom II X3 720, and use an ATI 4850 video card. Not quite the performance of the X4s and 4870, but it would play IL2 quite well. The only disadvantage to this would be that it may not be good enough for SOW, if/when it's released.