AlexNovember :
My biggest concern is going to be the longevity of the components. I've read that it's futile to ask how long these parts will be relevant, but what is your opinion?
Well the GPU can last quite a long time, its an r9 390 after all, good gpu. The CPU fx8350 should be able to push 2 years as well, same as any intel CPU you get for the same budget (even lower since you have to get a motherboard as well). Personally I would go just for a GPU and see how well games run. If you are satisfied with the performance you can keep your CPU for a little longer till your budget is better.