Wireless box ? Do you mean a router. If so that's one to leave on, as it takes time to establish best line speeds etc.
PC/Printer/Monitor I would switch off.
Every watt you burn on a 24 hour basis very very approximately costs 1 pound per year. So that printer that (perhaps) uses 6 watts in standby costs £6 a year to keep plugged in doing nothing.
You can get energy monitors that you plug everything into and it will show how much is/has been used.