I agree, airflow is not much of an issue, usually only 2 fans will do fine, and your case ships with 3 fans already.
If you cannot afford anything more than a GTX 750Ti, consider the R9 370, it is in the same price range but performs better.
Also the difference in gaming with the CPU will be minimal, you will not notice much difference with a 4460 and a 4690K, especially when using a lower end GPU. Only on high resolutions (1440p or more) and high end GPU will there be a noticeable difference.