Bare minimum, yes. While many feel ok running a psu @ 80% or so of max rating, I personally don't. I prefer running about 60-70% of max rated output for a couple reasons. First, the total power rating of the psu will include not only the 12V we're interested in, but also the 5V rail which isn't insignificant. Second, you tend to hit the sweet spot in efficiency around 60% of max output. And third, if you're not red-lining the power it tends to run cooler and longer before possible failure.
Just my .02
BTC, but I am a German born engineer, so take that for what it's worth...
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