Speakers on shelf
Keep in mind that if the 6" dimension is due to a shelf height, that the enclosed area around the speaker will effect its ability to perform properly. Your best bet is a matching paradigm on a bracket above the display. Also, the center channel is very important to HT.
If you are willing to make major compromises in tonal matching. You might hook up the TV's powered speakers to the mono center output and see how it sounds.