Great Article
It all depends on what you are shooting. Creativity is a HUGE factor, but when you talk about Sports (or anything with a lot of motion) or low light, the more expensive cameras will give you an edge. (e.g. Larger sensors, better ISO, AF tracking, and frames per second). I have both a 1dx and a 5DIV, I love the 5d and i use it 90% of the time.
You are absolutely correct about the 50 1.8 - I had a professor once tell us to use that lens and it will help you out tremendously - especially getting used to getting up close to your subject (which may be intimidating for some- as was I).