Placement of Center Channel Speaker

Fernando- Easiest way to match the center speaker to the main L and R speakers is to ditch the center speaker altogether and use the "phantom" center channel mode in your processor or receiver. No problems with "height" match, no problems with "tonal" match, etc., etc.. And viewers sitting off to the sides will have the sound "anchored" to the screen if your mains are half-way decent at imaging.

Should be level up with your L & R speajkers on top or right under your TV. Angle the speaker is a good idea.

The best way to angle the center speaker is to temporarily stick a little mirror on the front baffle sit down at the sweet spot and have someone angling it until you see your entire face in the mirror.

Exertfluffer, what tweaks have you tried to deal with the chesty sound issue?

Would like to know here also...

DSK and "infinity audio", for the most part, an easy wasy to improve on the sound of a speaker placed on top of a TV is to "de-couple" it a bit, by using "isolation platforms"(Lovan's "tri-solater is one), which many companies offer! You can also put points, and other issolation devices between the speaker and the TV, but I think more solid is better. Simply laying a speaker on top of a TV gives too much dirrect contact and surface area with which to transfer vibrations from the speaker cabinet to the TV cabinet! Yes, a less than stout TV box will take sounds from the system itself, and reasonate them into the TV, ading sound to the room, which isn't desireable. But, it's small compared to having a speaker laying up against a set, which magnifies the problem!
Anything really(even "sticky tack", or "blue tack" between your speaker and your bigscreen will help somewhat, and also help anchor your speaker for sound and stability. But, I think it's better to issolate them even more.
Anyway, that's probably the biggest thing you can do to issolate sound from mixing between your speakers and your TV! Note: your center speaker and your TV, when mixed together, become one larger speaker resonator!
Just lay against someones chest while you're talking, and hear your sound echoing through their body some time!...it's the same kind of issue.