Not the A4 Jetta. The comparable B5 / B5.5 Passat has a wider rear track spacing and the seats aren't plug&play into the A4 Golf/Jetta.
You might wish to consider the foam of the cloth GL/GLS A4 as that appears to be less dense than the foam used in the leather covered GLS/GLX/GLI if you wish for 'softer', but I think you'll be unhappy, (unhappy-er) with that.
Buy a used cloth seat and try it for a while to decide before stripping the leather and replacing the foam with the foam from a cloth seat.