The thing with the RAM is that it needs to be able to clock higher with the FSB if you are going to overclock the CPU. Do not get me wrong, G-skill is on the top of my list for RAM these days due to price/performance ratio. Heat Spreaders help with some memory especially when overclocking is taking place although it just depends on the RAM. It often times is just for show. I am just thinking price for Mags since this thing is a little over price. I picked that case because the one you chose looks to be small which will make the newer video cards impossible to fit. Usually the PSU's that come with cases suck to boot.
I chose a better Video Card because of the fact that Valve is always updating the Source Engine and with Episode 2 coming out soon along with Team Fortress 2 and Portal, a little better video card would be the best way to go. It's not all about DX10, it's about Nvidia's new design which newer and newer games can benefit from, including CSS.
The Overclock for Mags should be easy and will turn a 600 dollar system into a 850 dollar system.