This is going to be totally unorganized because I'm doing it at work so sorry in advance!
The Wolfdale 3.0 GHz will run most games better than that 2.4 GHz quad. Maybe even ALL games better. Don't underestimate high end Core 2 Duos. If it was me I would be buying the 3.0 GHz Wolfdale.
I think the power supply mentioned is overkill. More than overkill actually...if you're not gonna OC, a quality 300w PSU will run
any system (sans SLI). No reason to spend $100+ on a PSU for a standard system like yours. This is what I would get:
Newegg.com - PC Power & Cooling Silencer PPCS370X 370W ATX12V 80 PLUS Certified Active PFC Power Supply - Power Supplies PC Power and Cooling 370w
The memory can be bought cheaper as well.
Newegg.com - CORSAIR 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory - Desktop Memory Corsair XMS 4 GB $70 before $25 mail in rebate, dirt cheap, high quality
The the money you saved there you could either keep it or upgrade the videocard to a Radeon HD 4850 which will run circles around the 9800 GT (though the 9800 GT is an excellent choice for the price and will blow the doors off of WoW).
Newegg.com - SAPPHIRE 100245L Radeon HD 4850 512MB 256-bit GDDR3 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card - Desktop Graphics / Video Cards $160 not counting the $20 mail in rebate
I agree with the CPU, motherboard, and DVD drive Luciferase picked out.
As for cases this is what I have and it's a dream come true:
http://www.newegg.com/Product/Produc...82E16811112099 Lian-Li, widely recognized as one of the best case manufacturers in the industry, $99
HDD: If you can afford it, go for a VelociRaptor HDD like Luciferase suggested, maybe a cheaper one:
Newegg.com - Western Digital VelociRaptor WD1500HLFS 150GB 10000 RPM 16MB Cache SATA 3.0Gb/s Hard Drive (bare drive) - Internal Hard Drives Or just get a freakin massive one for half the price. I have a Raptor in my PC and I'm not sure I can tell a huge difference but it has been a while since I played PC games without a Raptor.
Keep asking questions if you're confused and don't buy on impulse because not everything is as it seems in the PC industry.