http://www.axiomaudio.com/power.html
Yeah, I've read that several times, and although I implicitly believe Alan on all subjects Audio, I still don't know how much is enough.
For example, I'm pretty sure that I need more that .5 watts per channel.
FWIW, I recently purchased one of those Radio Shack SPL Meters and I was surprised. I really thought that to me, loud music would measure over 100 db's -- maybe it's just some macho thing. What surprised me, was that "reasonably loud" was only 85db's and "pretty damn loud" was just 90db's. At that level, my HK3480 (120wpc) had lots of room left on the volume dial...
