What size amplifier do I need?

["martinchambers17" <MartinLChambers@xxxxxxxxxxx>]

As an audio novice I can't get my head round what power amplifier I
need for my whole house audio system. The system I'm planning will
take speaker level output from my hi-fi into a 4ohm amp which is then
connected via a central hub to volume controls in the various rooms
with speaker wire. The volume controls use a step down transformer to
maintain a constant impedance back to the amplifier at all times. The
sum impedance of all volume controls matches the impedance of the
stereo amplifier (i.e. 4ohms). The speakers will be 8ohm, 30w RMS/60w
peak. A Maximum of 8 Volume Controls can be connected. I plan to wire
up 8 rooms but expect no more than 4 will be used simultaneously -
and that will be rarely. Low volume will be the general rule but the
system should cope with the accasional party.

Any help would be greatly appreciated, Martin