There is some pride, fun, and learning that goes with building your own. Ya really become one with it. Motherboard and power supply will dictate what you can do with it, leaving room to upgrade it in the future.
Selection of case, MB, power supply and cooling. The rest is pretty easy.
People in the Hardware forum are usually more than willing to help you. Very knowledgeable ppl.
Its a personal choice. Not everyone is into it. Until recently, lack of time, I always built my own, since late 80s.