^ This post. 100%. Except I have an i7 for video rendering but that's besides the point. If you want to game properly, get a PC. It gives you experience and while Mac graphics do get better, they're still not great at PC games.Maybe I'm getting really old, but your original post made me grin.
None of your needs require such a machine (especially that amount of RAM, ouch). For the games you specified and school usage, almost any MacBook will suffice. There are better ways to spend that money than on computer you won't be able to utilize in 20% (except for GPU).
In general, for playing games, you would do really well to buy a PC or preferably build it yourself. I also love Macs but the GPUs are simply underpowered for heavy games. Remember, that if you get top-end iMac, your GPU is still worse than any 200$-250$ GPU on the market and it also has to drive higher resolution display than usual Full HD (27" Macs are 2560x1440).
As much as I hate Windows, you really can't say that versions 7 and 8 are unstable. UI and usability is bad but they won't hang up unless you put bloatware on them or break them yourself on purpose (aka playing with registry). Besides, if you build PC yourself:
1) you learn something new
2) you get OS without bloatware
3) you get better gaming machine
I wish Apple made machine strictly for gaming purposes but this day hasn't come yet.
PS.: Desktop i7 processors benefit literally nothing to gaming except for maybe one title - Crysis 3. The difference between i5 is just Hyper Threading technology which is simply not used in gaming industry.
At Uni I'm bringing my Desktop PC and either a Surface Pro 3 or rMBP 13". PC will *probably* just gather dust, but yeah