Hardware noob here: If I wanted to disable integrated graphics and add an additional GPU, would the only thing I need be the proper bios and a power supply that could handle it, or do I need something else?
Exactly. I've taken all of those into account. My CPU choice is limited, but I can deal with it. My APU/CPU choice + GPU will be slightly bottlenecked, but not by an obvious amount.
You should put something up with your planned build before you build, some of us may be able to give you some advice especially if this is your first time doing something like this. The market changes all the time and you may be able to afford a better gpu then you think you can.