We have tried flipping the speaker cables (Kimber TC8) at both ends.
I am not sure what this accomlished? Did you do it on both speakers? Maybe you can clairify exactely what you did with them?
We have replaced or substituted the cables from the pre to power.
Again, this will do nothing.
We have settled on the "phase" that sounds right.
Maybe one of your speaker was in fact out of phase with the other, not witht he actual signal itself.
Besides, you have no idea what phase is the correct phase as in the recording, the absolute phase is not in anyones mind to follow.
And, as was stated, you need very special signals and conditions to observ this issue, certainly not in music. You should expand your horizon and read some of the works of RA Greiner who followed up on Johnsons poor work.