I've bought a marine CD/Stereo unit (Jensen MCD5112) to install in a
swimming pool building in Australia and am stumped as to how to choose the
most economical 240 VAC/12 VDC power supply for it and would appreciate any
advice.

The unit is intended to be powered by a boat's 12 VDC system but I have 240
VAC available. I thought the stereo would be a good one for the moist
environment in the pool house.
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Specifications for the stereo a
Amplifier--
Total System Power 200 W peak
Power Output 4x50 W
General--
Power Supply 11-16 VDC, negative ground
Speaker Output Impedance 4-8 Ohms
Fuse Fast Blow ATO (15 amp)
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I planned to connect a pair of indoor/outdoor speakers and can choose
between:
30 W rms, 8 Ohm or 25 W rms, 4 Ohm
The 25 W pair have slightly better sensitivity and frequency specs and cost
a little more.

A label on the stereo unit states, "The amplifiers in this radio are only
designed for use with 4 speakers." I don't know if this means it cannot be
used with just two speakers, or that you cannot connect more than four. I
was only planning to connect two.

My questions a
1. How small of a power supply can I safely get by with? If I choose the
choose the 25 watt speakers, and find a 80% efficiency, 150 W power supply
would that be sufficient?
2. If the label does mean I need to connect four speakers, can I instead
connect two and substitute appropriate size 4 Ohm resistors for the other
two?

Thanks.