Martin Logan doesn't say not to place the Stage on a wall, and all it says is to tilt it directly towards the listener's ears. That's exactly what I did.
Unfortunately, most manufacturer's manuals (including ML's) have only the most basic setup information to guide you, and it is designed more to provide versatility for different setups rather than optimum sound quality. Sometimes they are more focused on appeal to the widest audience than achieving the best sound quality. Case in point: adjustable spikes that allow you to adjust the rake angle of the panel on the newer speakers. ML didn't provide this on the Summit when it came out. But after Jason on this site started providing longer rear spikes and we all realized that a vertical rake on these speakers provided better sound, ML learned from us and finally adopted this strategy on the Summit X. It is great that they realized this need and came around, but it just showed that you can't always rely on what the manufacturer says and does in order to get the best sound.
An audiophile seeking the best sound must have an understanding of sound wave physics and (for ML's) dipole speaker radiation patterns in order to tweak their setup to sound its best. To someone who understands those things, it is clear that the center channel needs to be on a similar plane and angle as the main speakers to achieve some coherence of sound. Also, things like distance from the wall behind it and absorption vs. diffusion vs. flat wall make a huge difference in the quality of the sound, especially with a dipole speaker.
In other words, simply because ML doesn't say not to place the Stage on the wall, or because they give you the option of placing it high or low and angling it toward the listener, doesn't mean that doing so will give you the best (or even adequate) sound. They are trying to provide the most versatility for different setups. But these extreme setup options definitely compromise sound quality.
My suggestion is that before you worry about purchasing a new TV, remove your current TV and bring the Stage down to rest where your TV currently sits, just below ear level and angled slightly up like your Spires, and just see if you get a better sound. The simple fact is that speaker setup requires a lot of trial and error to find the best positions and angles for proper sound. If you do find an improvement, then you have an idea of the direction you need to move in your setup.
