i built my own.

I've always thought about building my own, but since I'm at college I can't really do that. I looked into it though. One thing I've always wondered is about the PSU. How do you know how many watts you need?

if it's just a regular computer, with maybe some light gaming, you shouldn't need more than 500w. if you're looking at watercooling, dual gpus, etc, then 750w+ it's always good to have some overhead in case you want to upgrade in the future. there's no harm in having too much power.