You can ignore all the higher priced options, just focus on the first rig, and use that as a guide to select your parts.
Oh yea. That base rig could give you gaming pleasure for the next 5 to 8 years, if you upgrade the video card every two or so years. Maybe add some more RAM at some point. I built a solid rig, much the same class of parts as that base rig for it's day, back in 2007 that I gamed on until a couple of months ago. All I changed was the video card.
Also, you don't have to get the exact parts. For example, a non SLI Mobo with all the good stuff can be 30 to 50 bucks less than the mobo specc'd. The chipset and features are the key to selecting a mobo. Sure, limiting your dual card options might not be something you want to do. But, a single good video card is usually a better option, and two good video cards is like a little better, if it works for that game. See this thread, and the article linked.
http://www.gamesas.com/topic/1447563-dual-gpus-not-that-good-a-solution/
For video cards, find the 7870 chipset for the lowest price, it does not matter really who makes it. Other than clock speeds, coolers and any game bundles, pick on price. My card came with new BioShock and Tomb Raider. That was a cool surprise as I bought my version for the cooler and clock speed.