Get the MSI MPG A1000G PCIE5 1000W instead, it usually sits right around 210 bucks and has been rock solid for me. In my experience over the years, MSI power supplies have gotten really reliable. You definitely want that native 12VHPWR connection so you dont stress about melted cables. 1000W is the sweet spot for a 4090 system, 850W is just too tight for power spikes.

To add to the point above: be super careful with transient spikes on these cards cause cheaper units will literally shut down your whole system mid-game. I went through that exact headache last month before upgrading. Here are two solid ones under your budget that wont give you a heart attack:

• Corsair RM1000x Shift 1000W 80+ Gold
• Side cables make cable management way easier, but just measure your case width first cause it needs extra clearance.
• be quiet! Dark Power 13 1000W 80+ Titanium
• Insanely quiet and efficient, though it pushes right against the top of your budget. Grab a 1000W ATX 3.0 unit and you wont have to stress about melting cables. Good luck getting it built before your time off!

Congrats on the 4090 pickup! You definitely want an ATX 3.0 unit with a dedicated 12VHPWR cable so you dont have to mess with those sketchy adapter dongles that came in the box. I would suggest picking up the Corsair RM1000e ATX 3.0 since it sits right in your budget around $180 and gives you plenty of headroom without melting anything.

Honestly dont mess around with an 850W for a 4090. Get the Seasonic Vertex GX-1000 1000W Gold ATX 3.0 instead, it usually runs right around 220 bucks and handles transients way better. I had issues with cheaper units tripping OCP under heavy load. That native 12VHPWR cable solves the melting worry too.