5.1 vs 7.1 for This Room

I think either layout A or C would work better than layout B, with a few suggestions: place the surrounds further apart (right surround in back right corner of the room, left surround where the wall starts on the back left), toe in the front speakers (a la layout A) so that they're pointed at the person on the opposite end of the couch, add some absorbtion to the right side wall to sound more consistent with the open left side.

I think it looks better. If you're still open to suggestions, I have a couple more (with explanations). That's fine for the mounting height of the surround speakers. I would mount them on the back wall, spread as wide apart as symmetrically possible.

I would also spread the front speakers further apart, with the left speaker at the edge of the front wall. The wider spread means that sounds on the left side of the soundstage will be to the left of the person on the left side of the couch rather than directly in front of them. Maintains left vs right directionality better for listeners outside the sweet spot.

The exaggerated toe-in (pointing each front speaker to the person on the opposite side of the couch), will keep the nearby speaker from dominating the soundstage and keep the far speaker from becoming relatively inaudible. The left speaker would normally be louder to the person on the left side of the couch, but by rotating it away, you attenuate the volume and compensate for the proximity. The right speaker would normally be much quieter to that same person on the left side of the couch, but by pointing it at that listener, you make it louder and compensate for the distance. It's an old trick, sometimes referred to as time-intensity trading. Can you move the seating further back, like in layouts A & C. This will still give you an over-30° viewing angle (as long as you stay within 8.5' viewing distance). As for TV height and centre speaker placement, I would strike a compromise between them.

Ideally, all three of your front speakers should be at ear height (36-40 inches). Of course you can't do that with your centre speaker if your TV is at that exact location. Our human vision tends to bias downward about 12° or so. If I stood you up in a flat landscape and asked you to look straight out, your natural tendency would be to see a bit more ground than sky.

Most 65" TVs are roughly 3' tall. Rather than mounting it centered at eye height, if you could move it down about 6-8" it would fit nicely with your natural field of view AND line up better with the faces on screen (which are usually composed in the top half to third of the image). Best part, it would allow you to place the centre speaker above the TV and be pretty close to ear height. Works well for picture and sound. It will work out fine and sound great. If your willing, I'll ask you for one more diagram. Start by placing the left surround speaker on the back wall, just after the gap (flush with the edge of the gap). The right surround speaker also goes on the back wall, where it meets the right wall (corner). Split the distance between them and make this the centre line of your set-up. Place the left front speaker at the edge of the front wall, just before the gap, and place the right front speaker the same distance from the centre line. Place the couch closer to the distance from the front wall you had it in diagrams A & C (or as close to that as you are willing). Finally, cross-toe the surround speakers like I suggested for the front speakers.

BTW, what receiver are you using?

That's the best that Panasonic makes. You might want to compare it to a similarly sized (64") Samsung plasma to find out whether you see much difference. If you don't then you could save some money by going with the Samsung. If you want to compare them, there is a whole section of the forum dedicated to plasma flat panel displays, where you can start a thread and ask questions. There's probably no other aspect of audio that is more dependent on personal preference than speakers. I usually audition speakers using a few recordings that I'm very familiar with. As with the plasma TV, there is a section of this forum dedicated to speakers, where you can start a thread to get recommendations within your budget. The only suggestion I would make is to get 2 subs. There is plenty of research demonstrating that multiple subwoofers help smoothen out the frequency response (fewer peaks and dips) AND improve consistency from seat to seat.

As for receiver, I would get something with good room correction, like the Denon AVR-4311 or Onkyo TX-NR818; the latter can be had at significant discounts, which would make it my first choice of the two, leaving more of your budget for speakers and subs. Like most modern receivers, they come with a microphone, which you move from seat to seat in order to do automatic calibration (set the speaker levels and distances) and automatic room correction (equalize away the room's unwanted contributions to the overall sound).

Looks awesome! Nice and symmetrical. Taking into account multiple listeners on the couch.

Moving the couch a bit forward would be a good idea, more for traffic flow than anything else (won't hurt the sound). At 8 feet your 65" display will still give you a good 33° viewing angle. Also, don't feel locked into the viewing distance. Once everything is installed, if you feel like moving the couch forward a bit, then don't hesitate to do so. The reason I keep using words like "about" or "roughly" or "around" is because there is nothing hypercritical about these placements. You won't have to sit in the sweet spot with your head in a vise to enjoy this system. Everyone on the couch will have an enjoyable experience. If you do settle on a different location for the couch a few months after install, things will still sound fine (just remember to re-run auto-calibration).

If you end up using bookshelf speakers mounted on the wall rather than tower speakers standing on the floor, then you can spread the subwoofers wider apart (like under your L/R speakers). With an irregularly shaped room like you have (and I have), the only way to know the optimal subwoofer locations is by measuring their combined frequency response. Short of that, spreading them apart will help. The room correction in the receiver will further help to smoothen the response. Down the road, consider bass traps for some of the corners. BTW, if you do wall mount your left & right speakers, try to get them to roughly the same height as your centre speaker; when a truck drives from across the screen, its sound won't move up and down as it pans from the left to centre to right speaker.

Did I mention your latest layout looks awesome?

Happy Thanksgiving to you too.

You're welcome. Good luck with the project.