Yet another newbie.

Basically I’ve stumbled my way into a modding web page and what can I say, I’m in love. My question is about the power. I’ve seen lots of groovy things I want to do and came up with a couple of my own ideas, but don’t want to drain my system of power. How do I know a device or a Molex connector  can handle extra LEDs, neon lights, or what ever I should decide to add in  with out under powering it ? Any websites or advice would be greatly appreciated.
.:OUT:.

What power supply are you using. Your best bet is to just get a good PSU. Chances are that your PSU can handle it just fine. Although, you never really know. I just blew a 430 watt enermax by using it to power a SCSI raid.