I'm finally building my dream gaming rig next month but I have no idea where to start with the power box part... my logic was just buy the biggest number but now I'm scared I'll get the wrong wires for the 4090. Is a 1000w unit okay or is that gonna blow up the i9-14900k?
1000W is plenty for that build. Just make sure you get an ATX 3.0 unit so you dont have to use those messy adapters for the card. I used the Corsair RM1000e 1000W 80+ Gold ATX 3.0 lately and it saved me a lot of money over the premium brands. TL;DR: 1000W is fine, just buy ATX 3.0 for the cables.
To add to the point above: 1000W is definitely the sweet spot. Going higher is basically a waste of cash unless you're doing hardcore overclocking.
Check the Cultists Network PSU Tier List and just get a Tier A unit. Im totally satisfied with my Seasonic VERTEX GX-1000 1000W 80+ Gold ATX 3.0 and its super reliable.