.....Virgil, if your Mom and Dad will view the TV from a couch or chairs in the middle about 15 feet from the TV, try placing your two mains out beside the TV on both sides, imaging at about 8 feet of stereo seperation, pointing to the location where your parents will sit....
.....elevate them, if at all possible, where they are imaging above the level of seated heads, and if possible, elevate the TV to be between the imaging....even one foot of raising the imaging, has an amazing effect for the chamber, and sure, too high is not good, and yes, you need a sub to correct and cover for the floor-standing mains not being on the floor.....
....if'n I had one sub and two mains, and that was it, the sub would go on the floor evenly split between the mains....and it would for sure be front-firing....and it would make the overall sound like the mains were doing it.....
.....and Virgil, Mom, for sure, won't want the pictures falling off the walls....but yeah, Dad will crank that sub when she's at the market.....
.....Buddy, I watched a "BIG" framed-picture about 4 feet wide with gold wood-frame disappear behind a plush couch one day, haha....whompy cornerhorns with bass tone-control at 5 o'clock, haha....LOUD....mercy....I'm glad those BIG mid-range metal horns are gone.....
.....Virgil, we'll expect a report......