If you consider Gaming for your rig, go for the Core2Duo, instead of the Core2Quad. There are only a few numbers of games that uses the Quad core technology, so there aren't any benefit in getting a quad core, especially Q6600 which is more than a year old. Go for the E8400, E8500, or E8600. Don't be amazed by the "Quad core"thingy because the E8400 is much faster, considerring 3.0Ghz Processor speed (meaning 1.5 Ghz per core, Q6600 has 600Mhz per core), 1.3Ghz FSB (Quad core has 800MHZ FSB). for the casing Gibabyte GXZ2 (if im not mistaken) is pretty decent and cheap. I have Nvidia 8800 Ultra 768Mb DDR3 Video card and it fits perfect. Consider buying a 750W modular PSU to support the PCI-E power requirement. Also, for the memory, go for Amazon. you can get a 4Gb OCZ with heat sink for QR420, includding shipping cost. Motherboard, go for Gigabyte EP45 series, which offers built in raid on their built in SATA, which speeds up the read/write response of your HDD.

Just my 2 cents.

It's not because things are difficult that we don't dare, it's because we don't dare that makes things difficult!