Soldato
You're right, they're not. But to muddy the waters even more, they recently started putting their badge on one or two good quality units. So it's a real minefield when it comes to power supplies. I tend to stick to the Seasonic or Corsair ones as most of those tend to be okay, there are one or two turds by both as well though.
OP, I'd agree with everyone else. Dual 40a rails probably equates to around 65a in real money and if the quality of the supply is questionable, then it won't sustain the load of a 3090. Go for one big single rail. That's what I've always done, this thing I have delivers 83a, just in case I install something power hungry. And if I don't, I have a whisper quiet system.
You can't link to competitors here, but you can get a make and model of something you're looking at and run it by people here. Woodsta seems very knowledgeable on this subject and will perhaps also weigh in with an opinion with any suggestions you make.
Cheers! But not as knowledgeable as I thought. Kit Guru says it's not a half bad PSU. https://www.kitguru.net/components/power-supplies/zardon/bitfenix-whisper-m-series-850w-psu-review/
3090 is beast though and they'll be some power demand with the monitor the OP bought AND a VR setup.
@EirePlane When you have the hard power off. Do you have to disconnect from the mains (toggle off at the PSU) to reset the PSU or does your monitor go black and your PC reboots to OS login?