I'm guessing we should have more info about the PC client after Yoshi's media trip. However, there was a screenshot of him playing the XIV beta on a mid level laptop so I imagine a gaming PC would be within reach for this game.
This article can give you an idea of what you can get with around $700. Personally I would go for an Intel processor but that will typically run you more. http://kotaku.com/5983493/how-to-build-a-great-gaming-pc-for-under-700