Voice and instrument image bunched in the middle??

It sounds like you are listening to a mono recording. If the recordings are old this may very well be the case. One thing you may want to try is to reverse the speaker cables on the binging posts of just 1 speaker and see how that sounds. If you are biwiring, switch both, but just on 1 speaker. Listing your equipment would also be a good idea.

The easiest way to check if the problem is coming from the room, is to just try the system in different room and see if you get the same results. Then you'll know for sure. If it does sound the same, I would try swapping out your components one at a time. If your problem is with one of your components, you're likely to find the one causing the problem.

If you still feel it may be the room, rotate your system 45 degrees. (Your listening chair will be pointed directly at a corner.)

"1)A contributor to the lack of focus, especially if it primarily has a vertical orientation, may simply be that the six foot listening distance is not enough for the drivers to blend properly. As you indicated, though, that is not the major issue at present."

I didn't think of that. When you sit too close to the speakers, they start to sound like headphones.

"Perhaps call your preamp manufacturer and ask them if your unit emits "phase correct" or "phase inverted"."

That's not the problem here. First, the difference is very subtle. Even if you have a preamp or source that allows you to change absolute phase, its very hard to hear differences on a consistent basis. Second, about half of the recordings released are absolute phase correct, and the other half are not. So even though the OP can't change this, he still has a 50% chance of hearing the recordings properly in phase.