I'm no expert. But I know I'm not bad at calculating wattage. With online tools. I'm installing my 4080 swaping out for my 3070TI later today or tomorrow. So I had to make sure I could run everything fine too. However I have a 1000W PSU. So I'm not worried.
I would personally be worried on 850W. Some online power calculators calculators have 4080s already. But the ones that don't you can safely choose
3080 from the drop down. They have about the same exact power requirements. 4080s seem to peak around 304 Watts. Some models like OC models may
go up to around 330ish? At least I believe that's what my research showed. And like you said power spikes can happen. However I've seen some reviews
that at least the 4090s where not having any major power spikes. I have not seen power spike tests for 4080s yet.
I tried a few power calculators for you
https://www.bequiet.com/en/psucalculator
I tried to configure your system as best as I could. It's reading around 800+ watts.
Possibly as high as 831?
However
https://outervision.com/power-supply-calculator is listing your power consumption
around 730W But it allows you to choose more exact parts like the fans and liquid coolers.
You know your system and exact parts better. Perhaps give these sites
a try and put in the exact information?
But these forums are full of savvy people who may just be able
to look at your part list and know if it will work. Obviously
850W seems like it could be enough?
But I would choose a 1000W for your build personally.
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