The chips on the A600 are surface mounted. Replacing the floppy controller chip could be quite a task. Hope you're handy with a soldering iron. Also, I think the floppy controller is in the Paula (Audio and I/O) chip on an Amiga 600. It doesn't have CIA chips. As far as I'm aware.
Edit: No wait. I've found a 8520PL (U8) chip by the floppy connector. It's listed as the CIA for the 600.