I would definately suggest you take a look at
EasyBCD as it shows a lot of hypothetical setups in the documentation and has specific options for MAC os.
btw I have had problems with Grub and vista in dual boot situations. none at all with easyBCD.
Another option of course in your situation with three HDD with an os on each is to use the Bios Disk Boot option
just switch the option on in the bios and select the correct drive to boot from when you boot, and no messy multi boot loaders
.