Here is the problem.
You can get a nice base computer within your budget, but probably nothing with a decent graphics card for gaming. All off-the-shelf low-cost computers come either with integrated graphics or very low-end graphics cards. Anything with a good gaming card will have the price inflated way up... major brand computer manufacturers like Dell, HP, Sony, Acer etc have ZERO incentive to hurt the sales of their high-end systems by offering low-cost computers with good enough graphics cards for gaming.
So you'll need to add a graphics card yourself, and unfortunately the only place to get decent prices for those is online.
For example, you could pick up this in person, it's much better than the Acer from Fry's:
http://www.bestbuy.com/site/Dell+-+Inspiron+Desktop+/+Intel%26%23174%3B+Core%26%23153%3B+i3+Processor+/+4GB+Memory/3152118.p?id=1218380502937&skuId=3152118&st=dell%20core%20i3%20desktop&cp=1&lp=5
This is another option:
http://www.bestbuy.com/site/Gateway+-+Desktop+/+Intel%26%23174%3B+Core%26%23153%3B+i3+Processor+/+6GB+Memory+/+1TB+Hard+Drive/3152445.p?id=1218380507379&skuId=3152445&st=gateway%20core%20i3%20desktop&cp=1&lp=1
The Core i3 2100 matches or beats most of AMD's quad-cores and 6-cores in gaming performance, it's a great budget CPU. But the system needs a graphics card- and Best Buy's prices on those are absurdly high.
Then order any of these online:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814131342
http://www.newegg.com/Product/Product.aspx?Item=N82E16814102934
http://www.newegg.com/Product/Product.aspx?Item=N82E16814150577
And you'd be fine for WoW on medium settings. All of those cards run fine on the factory 300W power supply (but anything higher-end would require replacing the factory psu)
Even with rush shipping, you'll do much better than Best Buy's prices on graphics cards- they charge $99 for $50 cards and $120 for $75 cards, stuff like that. Just turn away from that aisle, maximum warp.
Here are results for Crysis 2 (much more demanding than WoW) on high settings:
http://www.tomshardware.com/reviews/radeon-hd-6570-radeon-hd-6670-turks,2925-5.html
Here's WoW on ULTRA- which cards in this price range can't hack except at really low resolutions. At high you'd see much better results and at medium, even moreso. The 6570 is just slightly slower than the 5670:
http://www.techpowerup.com/reviews/Zotac/GeForce_GT_520/18.html
For reference, that Acer's Radeon HD 4250 is below the bottom card on this chart:
http://www.techspot.com/review/245-ati-radeon-hd-5570/page6.html
If you absolutely insist upon buying a graphics card in-store, Fry's has a GT 440 (fast GDDR5 model) for $90 out the door, down to $70 after rebate. Not a great deal since it performs identically to the cheaper Radeon HD 6570, but at least you could eliminate shipping delay.
http://www.frys.com/product/6553053
If you don't mind driving, there's a Best Buy directly across the street from the El Segundo Fry's. You could hit both places, provided the stores have the items in stock.
By the way, I recommend the Dell over the Acer because Dell's factory psu is 300 watts... Gateway's isn't listed- it might be 300W but might only be 250W, which couldn't support anything above a Radeon HD 6450 or GeForce GT 520.
CPU performance:
http://www.anandtech.com/show/4083/the-sandy-bridge-review-intel-core-i7-2600k-i5-2500k-core-i3-2100-tested/20