[SmG Drago]

It is your choice if you want to buy a Pre-built PC or build your own PC:

you can buy prebuilt since you are mostly guaranteed with the PC working and warranty shouldnt be an issue, the only bad side is just the price.
for Pre-built Desktops, there is a few "gaming" desktops
Alienware: If you want to show off
Origin PC: If you want to show off that sick interiors
MainGear: If you want to show off that sick interiors
Other Custom PC Builds: If you want to show off that sick interiors or have a sleeper agent

Building a Desktop will require more R&D(Research and Development) of your desired parts that you will need in order to get a better understanding of how the Computer works in a basic fashion . The only "down side" is that it will take time and if you mess up, you'll have to find the problem all over again, but it will be an unforgettable experience.