Speaker System Compatibility Issues

I recently hooked up a new Home Theater System for a neighbor in the main room. They asked me to connect existing ceiling mounted speakers (with transformer based volume controls) in two remote rooms so they could listen to music channels in those rooms. I connected a speaker switch to the "B" speaker terminals of the amp and connected the remote rooms to the speaker switch. The problem I am experiencing is that the two speaker systems are so mismatched that normal listening levels in the main room produce almost no volume in the remote rooms. If I shut down the "A" speakers in the main room, I have to turn the volume control so high to get acceptable listening levels that if the user forgets to turn the volume down again before switching on the "A" speakers, they will most likely blow out. Has anyone experienced this before and what can I do to correct this?