If all you care to do is max settings on WOW on tiny raids (never played it, but I did play in EQ in 150 man raids) then a solid micro board with 1 video card and 2 RAM slots is going to be good enough.
This board for $75 should be good enough
ASUS P8H61-M LE/CSM (REV 3.0) LGA 1155 Intel H61 Micro ATX Intel Motherboard
http://www.newegg.com/Product/Product.aspx?Item=N82E16813131724
Next is the processor. You have the budget for it so you might as well go straight to a 2500k for $220.
Intel Core i5-2500K Sandy Bridge 3.3GHz (3.7GHz Turbo Boost) LGA 1155 95W Quad-Core Desktop Processor Intel HD Graphics 3000 BX80623I52500K
http://www.newegg.com/Product/Product.aspx?Item=N82E16819115072
As for RAM, you will want the standard 8GBs, as with this product for $30
G.SKILL Ripjaws X Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model F3-12800CL9D-8GBXL
http://www.newegg.com/Product/Product.aspx?Item=N82E16820231428
You will want to keep everything cool and have a lot of room for cable management and fans and stuff. I personally like my case a lot and I would suggest it for this application too.
LIAN LI Lancool PC-K59 Black Steel ATX Mid Tower Computer Case
http://www.newegg.com/Product/Product.aspx?Item=N82E16811112319&Tpk=pc%20k59
It sucks that you can't get it for $60 anymore since that was a 1 day cyber monday thing, but its still a good case for $100.
Not sure if you intended to have a monitor with this, but the budget is fine with one so I will suggest one anyway.
ViewSonic VA2448m-LED Black 24" Full HD LED Backlight LCD Monitor w/Speakers 300 cd/m2 DC 10,000,000:1 (1,000:1)
http://www.newegg.com/Product/Product.aspx?Item=N82E16824116478
You will need Windows 7 64 bit which will run you about $110
http://www.newegg.com/Product/Product.aspx?Item=N82E16832116713
It isn't a full version, but it is documented here and there on the internet how to install the full version off of an upgrade CD so it should be good enough.
The keyboard and mouse exact models aren't that big of a deal, but lets say you want to go fancy and we can budget $50 for both together.
That is about $780 shipped so far
This build doesn't have room for multiple video cards so a mid range PSU is good enough, like this one for $73
Antec BP550 Plus 550W Continuous Power ATX12V V2.2 80 PLUS Certified Modular Active PFC Power Supply
http://www.newegg.com/Product/Product.aspx?Item=N82E16817371016
Antec is a really good PSU brand and you can trust it will perform like the label says and it is modular as well for good cable management.
The CD/DVD drive doesn't matter too much, I will just call that $30 and be done with it. You can get something for that easily that will be a good maker and model.
Hard drives are a big expensive right now so I will just stick with a good brand 1TB for $148
SAMSUNG EcoGreen F2 HD103SI 1TB 5400 RPM 32MB Cache SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive
That gives you about $400 - $600 left to pour into a video card. A 6950 is a really good deal at $250 after Rebate so I will go with that
XFX HD-695X-CDFC Radeon HD 6950 2GB 256-bit GDDR5 PCI Express 2.1 x16 HDCP Ready CrossFireX Support Video Card with Eyefinity
http://www.newegg.com/Product/Product.aspx?Item=N82E16814150549
You also get a free Dirt 3 game with it. I have it from when I recently bought my card and I like the game, personally.
You need wireless capability so here is a micro antenna for $10
Rosewill RNX-MiniN1 (RWLD-110001) Wireless-N 2.0 Dongle (1T1R) IEEE 802.11b/g/n, USB2.0 Up to 150Mbps Data Rates, WEP 64/128, WPA/WPA2, and IEEE 802.1x
http://www.newegg.com/Product/Product.aspx?Item=N82E16833166052
That is about $1300 worth of PC right there including a monitor and windows and all that stuff.
You can use the extra to potentially buy a SSD for your boot drive and programs to ensure quick load times on things if you want or you can just save it for games or something instead.