Front Stage Advise

My home theater is smaller, however there are two important considerations for the front speakers.

1. CENTER DIALOG HEIGHT. very good center, very close to the image, to anchor the dialog/center sounds to the screen not the speaker’s height if too far above or below.

Your mains do not do these sounds in surround modes, the coding strips those frequencies, takes signals out of the mains as the director intended,

Thus the mains do NOT always make a phantom center image as they always do in 2 channel mode.

2. WIDE center image from mains, especially when full range is sent to them and they do make both distinct l/r and create phantom center/slightly l/r.

This is important for both 5.1 and very important in 2 channel mode. A lot of programs are still 2 channel, the cable box and/or your AVR inadvertently make pseudo surround. I often go to 2 channel and find improvement, thus pseudo center more important.

I do not know what is out there, I got these way back when, I suggest you read about their method of achieving a wide center image, then ask questions about current front wide imaging.

http://www.hifi-classic.net/review/dbx-soundfield-100-135.html

I'll try saying it differently.

home theater is complicated, especially when using HT in 2 channel stereo mode (both 2 channel video and 2 channel music only).

Surround sound (recorded/streamed/reproduced right) is terrific. However, much streaming video sounds better in 2 channel mode. Learn how to over-ride the decoder when something is not great, to select/listen to 2 channel, stay or back to surround (you will be surprised). Knowing this, more frequent use of 2 channel mode, influences your selection of front l/r mains.
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2 Channel Video, or 2 channel stereo, center speaker is OFF
MUSIC: Dedicated listening spot needs a narrower center image
VIDEO: needs to create a WIDE center image, i.e. 3 people on a couch.
Thus, choose front l/r mains, and position them accordingly. 
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Center speaker HEIGHT. Any surround mode: center channel is definitely needed, and it's height location is very important to connect the dialog to the image. I find just below the image most successful with my small HT 55" monitor. Other's can discuss their solutions for very large screens to get the dialog height correct. 

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SUB(s) can be great, 

CROSSOVER where? in AVR; in SUB; Separate component?
Always ON, or Sometimes OFF, depends on connection method.
Thus, choose your mains' bass capabilities accordingly.

ONE SUB, omni-directional, position anywhere that works
TWO SUBS, directional, near front l/r, preserve imaging i.e. Bass Player's location, dinosaur coming from which side?

simple, right?