Multi-room sound equipment

[Howard Phelan]

I am wanting to configure my home stereo so that I can have speakers
in each room and on the back porch with individual volume controls at
each location. My stereo system has A/B outputs, but I don't think
that I want to use those because in my system when you activate the B
speakers, the A speaker output is mixed down to just the left and
right and will not go out to the rest of the surround speakers in the
family room.
What piece of equipment do I need in order to accomplish this? I know
there are in line volume controls available, but what sort of control
device do I need to split the signal out to the rooms?

Thanks in advance,

Howard Phelan