Jacques, in the past I did a fair amount of experimenting with a phantom center and found it very satisfactory in the circumstances you describe. Two advantages of a separate center speaker are that the center image is anchored to the center even for listening off the center axis and that the ability to increase the center volume independent of the mains helps with low-level movie dialog. Neither of these appear to be significant for you. You report no problem with hearing dialog and you're positioned in the center anyway.

If a listener to the phantom center moves to the side the image stays in front of him and also moves to the side, but no farther out than the speaker on that side.

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Enjoy the music, not the equipment.