Psu for 500/600$ is a good deal?

I'm building a new PC with a 9550x and 4090. My current power supply is the Corsair Ax1200, and looking around, I've seen 1500-watt power supplies ranging from £300 to £600. Does it make sense to change the power supply if it still works, or is it just a waste of money? Is it worth spending more, or is it better to go for something in between?