electro_neanderthal :
In all fairness, you never said what your server was doing, and the majority of all servers are designed to stress the CPU as little as possible. Folding, now that you've mentioned it, is very stressing. Also, I argued against a 500W, not a 550W. Call me paranoid, but my experience with PSUs has been different from yours, and apparently I just get unlucky with PSUs, so I always plan a large overhead just in case.
I do believe your experience, and apologize for assuming you were running a website. And it's great if you and others have had a solid experience with a 980 Ti and a 550W unit. In my experience, a 1000W unit failed to power a dual 980 Ti mining rig... and mining doesn't take as much power as standard gaming.
So, I don't mean to discredit your experience, and am not attempting to do so; but you can't really discredit mine or others' experience either. All PC components, even good ones, aren't the same.
But I did say the words "full load' its kinda safe to assume since I'm not a newbie here (hence the moderator tag) I know how to "fully load" a system.
I agree this 500w while 98% of the time may work fine, for the 2% of the time you'll get spikes, it won't, it will crash. A GOOD 550w unit, as I said though, can take those spikes no problem.
As for the 1000w unit failing on you, I believe you but anything can and will fail. But it probably wasn't due to wattage, theres any number of things that can go wrong to cause a PSU failure, and overdrawing them is only one of those things. Unless you were monitoring the power load at the time of failure you can't say the GPUs over drew it and broke it.
I swear by Seasonic, but I got 2 defective XFX TS PSUs once (made by Seasonic) and when i built my current system the Prime Titanium I got had a broken wire in the 24 pin connector. It happens. I'm since very happy with my replacement.