Just go to the manufacturers' homepages and look up their maximum power consumption, add and a percentage (maybe 50%) to figure out what you should get. Remember that cooling and overclocking use power as well. Your new PC sounds so weak though that even the used 600W PSU allows for some small upgrades, f ex RAM, HDDs and CPU.
Originally Posted by ChopSuey
You can often change the PSU fairly easily without taking out anything first. What you want to avoid with the PSU is use too close to its potential as it might crash your computer from time to time and get worse over time as it degrades.
Originally Posted by Bainwalker
My previous PSU is still good as well. Been under heavy use for YEARS.
Originally Posted by Abaratican
Maybe the cheap shit breaks down.
My 1300 PSU comes with a 6 year warranty. I'll prob be on my next one by then due to hardware changes or w/e that it doesn't support.