I agree with Larry's suggestion. If you are only looking for local volume control and not source selection, a 70V system is the way to go. You can get some pretty good sounding 70V speakers these days from the likes of JBL and others, in addition to the 8" round ceiling mounted models we all know and love. Really, almost any speaker can be used if you buy the transformer for it. The secondary is designed to drive 8 ohm loads. Most 70V systems are set up for monaural operation. They can be made stereo, but this is not common. Check out the ISAT series of amps from QSC audio.
If you want multi-room source selection and volume control, I'd look into an A-bus based system, manufactured by several companies including Russound, OnQ and others.