Go straight to the 9800X3D. Forget 7800X3D at this point. It sells for the same price here anyway… but the 9800X3D outperforms the 7800X3D easily.
You NEED DDR5 for it!
EDIT: currently, in my shop where i bought the 9800X3D, the 7800X3D is even more expensive 
I upgraded from the 7800X3D and it was absolutely worth it.