It's OK. For RAMs, I would choose from http://www.gskill.com/configurator2.php?pid=2&model=154...
2x4GB kit, 1866MHz, 1.5V or 1.35V.
Make sure that they would fit under the CPU heatsink
So, what else? a CPU heatsink, SSD, HDD, DVD drive, monitor, Windows 7 or Windows 8 64-bit. And a case and power supply, of course.
You can buy "kits" which include the motherboard, CPU and RAM. I have found this is usually a good option to go for as it guarantees that all these hardware parts are going to work very nicely with each other. It also cuts out a lot of research before hand, as you probably know, all CPUs do not work with all motherboards, and that counts for the RAM as well. This is of course sometimes a very exciting thing to do - matching up and CPU with a motherboard and then finding that it works a treat. But I find it very useful to buy these kits as it saves time and you know it's going to run smoothly.
I would also recommend a 5.1 sound card. As you are building the "Ultimate Gaming PC", sound plays a vital part in the immersion of a game. However some motherboards these days do already come with integrated 5.1 sound chips so have a look at that first.
One more thing to look out for is 64bit capability of your hardware. This shouldn't really prove an issue, but when I upgraded my system to 64bit my machine would just hang for no apparent reason. No error message or anything just freeze up completely to the point of me having to force it off with the power button. After extensive testing and troubleshooting, it turned out to be my internal WiFi card was not 64bit compatible and was causing the issue.