It depends what you will be doing with the PC. The wattage you specify for the components are all max draws. You will need to be mining monero on the CPU, an altcoin on the vid card, and torrenting terabytes of data a month to start to draw that kind of power.

But do note, the components will surge when booting up from cold. However, the S3 will not draw 300+ W immediately when turning on because it will be initializing its runtime and waiting to receive work if mining a pool.

While you definitely can do it, keep in mind that PSUs are most efficient on 50-70% load. And if it is a cheap PSU, working it at 90%+ will wear it out a bit faster.