Maybe the OP just wants a machine that can handle casual PC gaming, in which case, the rMBP or top of the line 2011 iMac, would be fine. I don't get all this talk about "buy a PC" or "build a gaming PC," because quite frankly, PCs are much more trouble than they are worth. Also, the OP can be heavily invested in the Apple ecosystem, which makes the point of buying a PC solely for gaming pointless. Apple machines can easily handle gaming (albeit not at extreme graphical settings even though that is somewhat not the case with Apple's utilization of Nvidia GPUs) and come with a OS that is a joy to use and excel in productivity.