PSU for a new build

[AusWolf]

The system is very unlikely to load both the CPU and GPU to the max at the same time - games that are CPU (multithread) bound/bottlenecked, if they do exist and max the CPU will in all likeliness drop the GPUs power, and vice versa.
I would assume that both the 3070 and the 5950X's power consumption will be within the ballpark of the 2080Ti and 3900X/3950X's, and W1zzard was kind enough to do total power consumption tests for the latter - the system will max out at about 400W draw at the wall.
While you may want to consider ordering a higher-specced PSU (if you don't already have one), the 550W-rated one will do just fine - it's certainly not worth spending another $200+ on a new PSU just for like, a 10% efficiency upgrade at 400W - you'd have to run your system at close to maximum power drawn for several years straight for your PSU investment to amortise.

Also, a 550W PSU is probaly safe enough to operate even for at 600-650W for a short timeframe in the unlikely event that your system really maxes out both the CPU and the GPU's power draw for whatever reason.

Thanks for the confirmation, I hope you're right. Thanks to the rest of you as well for the valuable input.

I think I've decided what I'm going to do. Presumably, the new Ryzen CPUs come out way before the RX 6900 XT (not to mention the unannounced 3070 Ti/Super), so I will buy the mobo, CPU, cooler and RAM first anyway. My 550 W Seasonic will be more than adequate to run all of this with my GT 1030 while I'm waiting for the new GPU. This will also give me plenty of time to test total system power consumption with the GT 1030 in it, so later I will have an idea of were I need to be in terms of PSU based on reviews of the new GPUs. If I'm fine, I'm fine. If not, I'll buy a new PSU together with the GPU.