Looking for opinion(s) for new gaming computer.

[Nottaclue]

To be brief, I have no experience building or knowing what's good in a computer. I currently have enough money ($500 - $600) and I'm looking to invest into a new gaming computer. It'll be my first one and I want it to last for awhile. I don't need perfection, just enough to get me by on games like WoW on medium - high graphics. I'm not looking to build my own computer either, just because of my lack of knowledge. I narrowed it down to 3 computers that I think would get the job done for what I'm looking for and found these 3 on Wal-Mart (yeah, sorry) and am just looking for opinions on which one would be the best investment. Any opinions are appreciated. Thanks a lot.

http://www.walmart.com/ip/iBUYPOWER-Black-Gamer-Power-WA550B-Desktop-PC-with-AMD-Quad-Core-FX-4300-Processor-8GB-Memory-1TB-Hard-Drive-and-Windows-7-Home-Premium-Monitor-Not/23745948

http://www.walmart.com/ip/iBUYPOWER-Gamer-WA563R7-Black-Desktop-PC-with-AMD-Six-Core-FX-6300-Vishera-Processor-8GB-Memory-1TB-Hard-Drive-and-Windows-8.1-Home-Premium-Monitor/35119953

http://www.walmart.com/ip/IBUYPOWER-Black-Gamer-WA560B-Desktop-PC-with-AMD-FX-6300-6-Core-Processor-8GB-Memory-1TB-Hard-Drive-and-Windows-8.1-Monitor-Not-Included/43155412

 

[Nottaclue]

I can buy from anywhere, these are just the first 3 I came across. I'm in a bit of a rush and like I said, have no knowledge of PCs so building my own is out of the question. My girlfriend has had her Ibuypower PC for the last 3 years and has ran it to the ground, but it's ran WoW and all her other games near perfectly for the time she's had it; hence the only reason I was looking at the Ibuypower brand. Any recommendations are appreciated.