Dude, I've got basically the same setup and literally went through this same internal debate last month! Honestly, for a 7800X3D and that beefy 7900 XTX, you're gonna want that extra headroom.

Here is what I found from my own build experience:

- I originally looked at 850W units, but once I saw those transient spikes on the GPU, I knew I had to go 1000W just for peace of mind.
- My current 1000W ATX 3.0 unit runs soooo quiet because it's never really stressed, which is a huge plus for noise levels!
- Buying the 1000W version was only like $20-$30 more than the 850W model I was eyeing, so the value for long-term safety is actually insane.

Seriously, just grab a Tier A 1000W unit and don't look back... it's better to have it and not need it, right?? gl with the build!

Seconding the recommendation above! 850W is honestly the sweet spot if ur trying to save some cash for games. I'm still kinda new to high-end builds, but i've been obsessed with finding the best value.

Check these out:

1. Thermaltake Toughpower GF3 850W 80+ Gold PCIe Gen 5 ATX 3.0 - It's usually cheaper than Corsair but still Tier A! Super stable for those XTX spikes.
2. MSI MPG A1000G PCIE5 1000W 80+ Gold Full Modular ATX 3.0 - If u find this on sale, it's amazing peace of mind for the future ngl!!

Both are fantastic and wont break the bank. GL with the build! 👍

Sooo +1 to what was said earlier about 850W being enough, but honestly, I was sooo paranoid about those XTX spikes when I started my build. I ended up grabbing the MSI MPG A1000G PCIE5 1000W 80+ Gold Full Modular Power Supply just for total peace of mind. It’s Tier A and basically silent. If you want a cheaper 850W safety pick, the be quiet! Pure Power 12 M 850W ATX 3.0 Fully Modular is super reliable too. Better safe than sorry, right? lol

Honestly, for your setup, a high-quality 850W unit is basically the sweet spot. The 7800X3D is crazy efficient, so you aren't pulling massive power there. I'm super happy with the Corsair RM850e (2023) Fully Modular Low-Noise ATX 3.0 in my build. It handles the XTX spikes no problem and usually goes for around $120. If you really want that extra peace of mind for like $30 more, the MSI MPG A1000G PCIE5 1000W Gold ATX 3.0 is a beast too. Personally, I'd save the cash and stick with 850W... it definitely works well!

TL;DR: 850W is plenty, but 1000W is safer for future-proofing.

Noted!

So, as someone who spends a lot of time testing rail stability, I always lean toward the cautious side with the XTX. Transient response is no joke, and while 850W is technically enough, seeing the ripple on an oscilloscope during high-load switching makes me advocate for a 1000W unit for DIY builds. It gives you a much better efficiency curve and way less thermal stress on the capacitors over the long haul. If youre doing the install yourself, cable flexibility and layout are huge for a clean build. I recently put a Seasonic VERTEX GX-1000 1000W 80+ Gold Fully Modular ATX 3.0 into a similar rig. Seasonic basically sets the industry standards for reliability, and their build quality is top-tier for DIYers. Another great self-service option is the Montech TITAN GOLD 1000W 80+ Gold ATX 3.0. It uses premium Japanese caps and handles those micro-spikes like a champ. Honestly, going 1000W keeps the PSU in its peak efficiency window and usually ensures the fan stays in zero-RPM mode during gaming. Better to have that safety margin for DIY peace of mind.