OK, so watts don't always equal volume. But for the most part, watts equal volume, so let's not nitpick it to death again.
I refuse to believe that a 300w amp that isn't anywhere near clipping isn't going to sound any better than a 500w or 1000w amp at the same volume. Watts are cheap, of course, so it's cool to have them if you want them, but come on...as long as you're not clipping, a high end low power amp designed to sound the same as a high end high power amp isn't going to sound any better. This was all explained to me last week by the power amp guys on here. Same with this hoo-ha about running an amp into an 8 ohm load vs a 4 ohm. The only way it would sound any better is because of clipping at higher volumes. At my volumes it sounds the same.
So while, yes, watts don't always equal volume, they have a lot to do with it.