Help with misc. parts

[oliminator]

Okay well here's the thing. I have the following PC:
Intel Core2Duo e6400 2.13GHz
Sapphire Radeon x1950XTX
2GB RAM 400MHz
P5NSLI Motherboard
Enermax 535W Power Supply
Any other information you need, tell me.

Here's the deal:
I am getting stuff for Christmas. So far I have gotten:
eVGA 8800GT Superclocked
Arctic Freezer 7

What else?:
I also am thinking of upgrading my case. Now I have some questions about that but will continue on later about this.

RAM:
I realize 400MHz RAM is bad, no? Now the max my motherboard can handle (pictured here: Newegg.com - Open Box: ASUS P5NSLI LGA 775 NVIDIA nForce 570 SLI Intel Edition ATX Intel Motherboard)
is 667MHz, correct? So in realizing this, do you think it would be smart to get a new 2GB of RAM @ 400MHz? Also, what do the whole PC2 6400, 8000, 5400 etc. numbers mean and how would I match up RAM with this motherboard? (At the bottom of post I have placed a link showing CPU-z RAM)

Case:
I have never built my own PC before, I actually had this computer built on CyberPowerPC. I have a very crappy case, was strapped for cash, and got the cheapest one possible (labeled as standard ATX case as seen here: Intel Core 2 Duo Custom Build Configurator Select ATX MEDIUM TOWER SILVER COLOR and you'll see). The thing is, I was wondering whether or not you would approve of me upgrading. Of course, you are going to say yes, but me being someone who has never built a PC before, would it basically be like putting a computer together? Or would I just have to unscrew a couple of things?

Overclocking:
I am getting an Arctic Freezer 7. So obviously I am going to want to OC my c2d. Now, you have read about the RAM and the Case, and so I ask, if I did not upgrade the RAM and the Case, would my OC be bottlenecked by the crappy case (heat) and the crappy RAM (do not plan on OCing RAM anyways)?

Thanks for any answers in the future! Also, if you feel I should upgrade my case and RAM, please post suggestions. Try and keep it low priced but better than I have.

Putfile - Uploaded Picture

[vernong1992]

the Board that will bottleneck..... its not the best overclocker...