Be sure to check the capacity of your power supply against the power usage
of all those disks. Not only could you run out of connectors, you could run
out of watts, resulting in irregular operation, unexpected shutdowns, and
especially CD-R calibration and write errors.
As a case in point, I have a CD-RW drive that works fine in one machine with
a 300W PS and one hard drive, but fails repeatedly in a similar machine with
a 240W PS and three hard drives.
I once read that the typical HDD uses about 60 watts starting up and only a
fraction of that afterward. That's old information even if true, but five
drives pulling 60 watts each at startup could shut down the rest of the
machine.
I agree that power consumption must be considered but 60W
could only be considered an instantaneous figure at most,
typically if you factor for at least 2A 12V per drive (and
the PSU amperage rating is honest, a big "if") it'll be
enough to get them spining in time to be detected by a
fast-enumerating board's bios. When the drives are
connected to an secondary controller that buys another
second or two at least for spin-up.
While spinning, they don't use all that much power relative
to anything else, most drives have max ratings on them. For
example the max on a Seagate 120GB sitting in front of me is
0.72A @ 5V & 0.35A @ 12V.
Even so, it should never be a goal to squeeze every last
watt out of a PSU, it'll run a lot longer given some margin.