PC best for FFXIV?

[Judge_Xero]

Could you recommend any that are better than those at the same price?

I'll see what I can do. I looked through all the ones on that Best Buy site and they are all terrible. I'll edit this post if I find something.

Would you be able to build it yourself, or does it have to be a pre-made PC?

Example of what you could build for that price range:
http://ca.pcpartpicker.com/p/MrmgK8 - without OS (add 100$)
http://ca.pcpartpicker.com/p/jqNqVn - with OS

You would probably want at least an i3 or AMD FX 4XXX series CPU
GPU - you should get at least an AMD R9 270 2GB or NVidia 750 ti 2 GB