ok this debate has gone on for longer than I've been a Polkie ;)
I recently added a old Pioneer two ch dual mono block amp and i'm testing it out right now on my computer rig speakers.. just in case it blows up, I don't want it to toast any other speakers. These speakers I could have die and I wouldn't even blink an eye. :p
Anyhow, the only thing I've changed this week is I added a big beefy amp. Let me tell you, even these crappy speakers are sounding decent.
So the old debate of which makes the biggest difference in a stereo rig has finally been settled, it's the amp of course. :D