If the price was lower, I'd have gone with a 4090.. But at $1089 I went with the XFX 7900 XTX. Eyefinity is better than 2d surround anyway. (it never drops a screen like Nvidia did.) Now that 24gb of VRAM will be to good use with 4Kx3 sim racing!!!!
www.techpowerup.com
That's not how it works with PSUs in the first place, and not how it works with physics. If you overload the PSU the voltage will drop and the card/system will crash, or the PSU will shut off, because one of its protections gets triggered... GPU performance does not go down in either scenario, the card doesn't even have a mechanism for "not enough power", which really means "too much voltage drop" .. and the Seasonic 850 W ATX 3.0 can take spikes well over 1000 W