Your post suggests that Pro-ject don't use "half decent" cables to begin with. The cables hard wired in are quite probably very good if Pro-ject has used them, and done their testing and tuning with them.
It's true that the cables from a turntable carry a fairly low level 'fragile' signal, and good IC's will certainly help, but don't automatically reject the cables that came fitted to the TT.
It's true that the cables from a turntable carry a fairly low level 'fragile' signal, and good IC's will certainly help, but don't automatically reject the cables that came fitted to the TT.