I guess you never know until you try, but if it's FireWire, that's enough. It should work. And if you want to put a nice new 7200RPM Ultra ATA drive inside your PowerMac, say, there's no problem there either.
CD drives aren't a problem, but CD burners could be, because the software you use to burn them must support it.
Fortunately if you're talking about expanding any of this through FireWire you also have the advantage that Macs are likely the largest consumers of FireWire devices, so you're not likely to find a company stupid enough to make a Windows-only FireWire device.