it all depends on what you listen to and at what level.
the most difficult tracks to play usually are some movies played at Ref. Level:

Super 8: 122 dB max - (446 W/ch. front L-R) / total Watts for my 6.1 setup is 1275 Watts.
WOTW: 122 dB max
300: 119 dB max
LOTR: 120 dB max
The Pacific: 119 dB max (L + R front only: 460 W/ch.)


if you can play those at Ref. Level, without clipping or distortion, then you have enough power to reproduce any music or movie. lots of music plays at 115 dB SPL or a bit less, when played at "live level".
if you usually set your volume at -10 dB or so, then you need much less power: 10 times less.

you also need a bit more Watts than your calculations indicate, just to be sure your amps will never clip.

check the link below my signature for more on my setup.

Hope it helps.