I am going to listen to the B&W 683's in a few days and I am also considering the Axiom M80's, but I am really confused about the whole 4 ohm and 8 ohm stuff.

The M80's are rated at 4 ohms which means it will be harder to drive than a 8 ohm speaker..... I really have no idea what that means though. Does that mean that I will have to put 100 watts into the M80's to get the same sound/volume I could get out of a 8 ohm speaker with only 50 watts?

If that is totally not accurate (which I suspect), could someone please explain it to me!