how much power

I do not have a good grip on amps. But i keep hearing about more power and more current !

I don't listen to music very loud... may be 75db at the most. The roomsize is 11 x 15. My speakers are Vienna Acoustics, Haydn Grand (4 ohm). Receiver is Denon 3311ci.

My question is really if i need need anything more than say 50 watts per channel ? Why ?