I have X-Omni's and an X-CS all with Ninja Master crossovers and No Rez. The detail level, soundstage, and imaging are great! These are a perfect match up front and my tweeters are all almost the same height.
When the av123 auction came along, I ended up buying 3 pairs of LS-6 cabinets. I started wondering what I would do for a center speaker. Danny suggested the OB-7 Plus without the bass section. After thinking for a while, I realized I had never asked myself if I "needed" the center speaker. I compared the center with center channel mixed back into the mains. As long as I am sitting within the width of the mains, I found that I like a phantom center better. Actually, sitting outside the width isn't even that bad. I used the Blu-ray of Cars to test the panning, soundstage, and detail. With point source speakers, the center is probably more important, but with the omni's and line source I would think that most would be happy without the center. No center also allows me to put my projector screen in a more optimum location.
Positives for no center: - Better dynamics of center channel material (could be due to using a more powerful amp for mains)
- Higher vertical soundstage for center channel material
- Smoother panning
- Less reflections from another source
- Perfect time alignment with center channel/mains
- Less vertical sweet spot (standing has less of an effect)
I am using an HTPC so I have more advanced control over channels than with a receiver. I can also quickly switch between phantom/no phantom center. Some receivers might have a worse implementation of phantom center than others.
You already have the LS-6's and may have tried a phantom center already.