Originally Posted by MrMezz
With 8-ohm speakers with a sensitivity of 88 dB/1 Watt/1 metre, and rear speakers rated at 8 ohms with a sensitivity of 89 dB/w 2.8v (1m), 130 watts should be more than enough. The actual results will vary by room (and speaker placement and seating location), but you can subtract 3 dB per extra meter you are from the speaker, and then calculate the sound level to get a rough idea of what you are likely to get. Assuming you are 2 meters from the speakers, you should get about 95 dB at 10 watts, which is quite loud. You should get about 105 dB with 100 watts (keeping in mind that we are talking about only one channel; each additional channel would add 3 dB to the figure, assuming the same efficiency speakers, and assuming that the sound from each speaker does not cancel out the other speakers due to being out of phase, etc.). If you were 3 meters from the speakers (you could not be that far from all of them in your room), we would be talking about approximately 82 dB at 1 watt, 92 dB at 10 watts, and 102 dB at 100 watts, with only one channel driven. As we are also talking about continuous power, your peaks should be able to be louder.
However, if you want to go deaf very quickly, then you might want more power (though you should be able to go deaf quickly enough with the 130 watts).
I have less power in a larger room, with speakers rated the same* impedance and sensitivity, and I can play it louder than I ever want, maintaining great clarity as loud as I can stand it. But if you are someone who listens to rock music at rock concert levels (which causes hearing loss, by the way), then you may require more power.
For more information on hearing loss and loud sounds, see:
*That is, rated the same as your front channel speakers, although, as we are talking about "nominal" impedance, and impedance varies with frequency, it may be that our speakers will not be capable of the exact same loudness with the same amplifier in the same room. Still, assuming that Gallo has not mislabeled their speakers, it should be close.
A fool and his money are soon parted.
Too many people seem to spend too much time reading between the lines for what is not there instead of paying attention to what is there.