If your power supply doesn't have removable cables, this obviously isn't an issue.
If you're using a modular power supply, you may want to plug all the cables you'll need into the back of the front of the power supply before inserting and installing it. Otherwise, you'll have to plug them in later from inside the case where it's hard to see the cable labels on the PSU. If your power supply doesn't have removable cables, this obviously isn't an issue.