Good for you for trying to understand this yourself practically rather than just reading articles.
And yes, you definitely need more than half a watt because there are peaks that must be accounted for. 90W should be adequate based on what you consider loud. I would say that if you listen to neo-classical, you may need 200W/channel. I have 90W and it is barely enough for some classical if I really want to make my 'nads shiver. However, since I don't listen to classical very often, I am not rushing out to get a new amp. 90W for me is over-kill for 99.9% of my needs.
