If I'm reading your description of the problem correctly, it sounds like something in your system may be broken.
"What I didn't really witness however, was the unbelievable imaging that everyone talks about, the image would waver from left to right and become sort of ubiquitous when it should be dead center. "
That type of thing shouldn't happen. It definitely sounds like a phase issue. The image should never move around like that. (Unless it moves around in the recording like when a singer walks around, or something similar.) If your wiring was wrong, and you were using a recording that you are familiar with, the voice will come from a different place, but it won't move around.
Its easy to check. Shut your amp off and go to just 1 of your speakers. Reverse the connections at the binding posts, black to red and red to black. If your speakers are biwired, do both pairs. That will make the speakers 180 degrees out of phase with each other. Play a recording with a center vocal and you will see that the voice is not between the speakers but more off to the side like it is comming from one of the walls. The point that I'm trying to make is that even though the imaging is not correct, it will not move around. The only situation I've ever heard where a fixed vocal image moves around is when it is done on purpose using a test CD. Its used as a demo to show what something out of phase sounds like.
Thats why I think something may be damaged. Since your SL3's sound OK, something may be wrong with your old speakers.
"What I didn't really witness however, was the unbelievable imaging that everyone talks about, the image would waver from left to right and become sort of ubiquitous when it should be dead center. "
That type of thing shouldn't happen. It definitely sounds like a phase issue. The image should never move around like that. (Unless it moves around in the recording like when a singer walks around, or something similar.) If your wiring was wrong, and you were using a recording that you are familiar with, the voice will come from a different place, but it won't move around.
Its easy to check. Shut your amp off and go to just 1 of your speakers. Reverse the connections at the binding posts, black to red and red to black. If your speakers are biwired, do both pairs. That will make the speakers 180 degrees out of phase with each other. Play a recording with a center vocal and you will see that the voice is not between the speakers but more off to the side like it is comming from one of the walls. The point that I'm trying to make is that even though the imaging is not correct, it will not move around. The only situation I've ever heard where a fixed vocal image moves around is when it is done on purpose using a test CD. Its used as a demo to show what something out of phase sounds like.
Thats why I think something may be damaged. Since your SL3's sound OK, something may be wrong with your old speakers.