They won't take up that much, it all depends on how many you have. I used to have a link to an online wattage calculator and it'd tell you the estimated power consumption of neon fans, cold cathodes, etc. But I lost the link. My bad.
Dude u dont have to worry about those kinda thing they take up less than minimal like 3 watts nothing. http://www.jscustompcs.com/power_supply/
try that and youll see how much they take up.