I auditioned the WP7s on a great many systems, and found them to yield a distinct presentation with each. My strongest recommendation to you is that you work with dealers that will permit you to audition the various combinations of equipment at home. I was only able to arrive at the presentation that pleased me the most after doing this.
That being said, I did have an experience similar to yours. I had originally matched the WP7s with Spectral electronics that I had loved intensely with the speakers that preceded them, but that did not yield the fine, textural detail of instruments and voices that I had heard elsewhere with the WP7s. I set about auditioning a lot of electronics and quickly found that I preferred tubes. Surprisingly, I found that I most enjoyed a set-up that was nowhere near the most expensive I auditioned. I spent some more time with other elements of the system (i.e. cabling, room treatment) to deal with small, but important musical issues, and arrived at a system that pleases me greatly.
As for your issues with imaging, I'm inclined to believe that this is an issue of speaker setup. Like many speakers on the contemporary scene, failure to set the speakers up properly can completely short circuit any attempt at realistic imaging. One of the great things about Wilson is that they have arrived at a highly reproducible formula for getting state of the art imaging. The problem is that it requires a well trained, dedicated individual to make this happen. If the person that set up your speakers left your listening room without the imaging being spot on, they are either inadequately trained, or don't care enough. My strongest recommendation is that you get someone from your dealership to come back out and set things up to your level of satisfaction. If they don't, call Wilson. They are manic about their product, and may be able to suggest a solution.
Good luck,
Siliab