Bare bones GPU upgrade?

[ElijahShow]

I am thinking on getting a bare bones PC, but I don't know the parts I have to add to one or if I can upgrade the GPU (it has integrated graphics). If you could answer these questions that would be terrific.
Here's the PC I'm thinking about:
http://www.ebay.com/itm/AMD-FX-6300-6-CORE-8GB-RAM-BAREBONE-GAMING-DESKTOP-PC-COMPUTER-SYSTEM-HDMI-USB3-/181918738417?hash=item2a5b33a7f1:g:mOIAAOSwxp9W3rCv

 

[CountMike]

It looks like it has standard MB with PCIe bus so any GPU would fit and work on it. There's no PSU specified so that can be limiting factor.