I think I see your problem. I'm not too familiar with your speakers so I did a search for them just out of curiosity. Unless I didn't look up the right speaker, it shows yours as having a single 12 inch driver per cabinet, and nothing else. On top of that, they appear to be vintage. Given the design and age of the speakers, I don't think you can expect the same type of imaging that you would get from a modern pair of speakers. Given the fact that I've never heard your speakers, I could very well be wrong, but I thought it worth mentioning. I know you tried other components with your speakers and got the same results. I think you need to try some other speakers. For testing purposes, all you would need is a cheap pair of bookshelf speakers. Maybe borrow a pair from a friend. You won't need them for more than a few minutes. If it is your speakers giving you the problem, you'll know right away.
