I have a Belkin wattage meter running on my tower.
Currently running:
CPU: Ryzen 9 5900X w/PBO (down-tuned)
RAM: 32GB DDR4 3600Hz G.Skill
GPU: RTX 2080Ti, not OC'd
M.2 PCIe 4 (WD SN850)
Dual 2.5" Samsung 850 EVO's
1x Seagate 3TB HDD
So long as I don't set my GPU's power limit above 100% (driver default is 130% max), I NEVER crack 500W.
I typically hit between 440-460W usage.
I'm very confident that you'll be able to run your system on that old PSU, just be sure to clear out the dust and use a GOOD surge protector on a properly grounded electrical outlet. This is key for PSU life and stability.
P.S. - I'm a retired system builder, built over 6K systems. I've seen dual GPU setups run on <1KW PSU's all day long for ~5 years. Age is another factor
P.P.S - The PSU in my current tower is 9 years old, CoolerMaster 750W Gold series. Gold series PSU's typically last much longer. Something to think about for the upgrade