On aminet there is a set of programs PC2AM308.LHA which allows you to access the PC's drives from the Amiga via parallel cable. It's seems to run about 20KB/s so at least it is faster than serial or floppy.
Is the A600's harddrive a 2.5" IDE? You can get an adaptor to use those drives in a regular PC for only a few bucks (compgeeks.com has 'em I think)
