You'd be better going for a Sandybridge build with a MSI P67A-GD53 (B3)
and either an Intel 2500K or a 2600K if planning on video editing at some stage. Either will overclock to high levels with a decent CPU heatsink and will outperform a i7 950
I doubt that there's any games that will make use of 24GB of RAM and only high end video editing or Photoshop are likely to come anywhere near close to using it. 8GB is probably more realistic.
Cases are a personal choice but a Corsair Obsidian 650D is pricey but quality.
A 650W PSU should be adequate and the Corsair HX650 is worth considering. If you plan on adding another Graphics card in SLI in the future then the HX850 should do it.
I'd suggest an SSD such as the 60GB OCZ Vertex 3 as your OS drive with something like a Samsung F3 or F4 as a data drive