Whoo boy. OK!
Well first up, thank you for replying with answers to the questions I asked. And those diagrams are great! Very helpful
I'm not sure where you were getting all of your info prior to coming to this forum. But sadly, it seems as though you've been led down some wrong paths. While it's true that having a large opening to the rest of the house will reduce standing waves, having that opening creates far, FAR more problems than it solves. Most obviously, you can't contain the sound what-so-ever to the theater with a permanent opening! What if you want to watch a movie, but your wife wants to take a nap? It also makes light control a nightmare. Do you really want a situation where, in order to watch a movie, no one can have a light on in the bar? And in terms of the audio itself, having a permanent opening means that you have to consider the entire area as part of the volume of freely moving air that makes up your theater. That's an utter nightmare for your subwoofers because your basement is very large!
No, if at all possibly, PLEASE enclose that room. You could have some nice, large french doors - preferrably solid core for soundproofing purposes, of course. Once the room is enclosed, the way to deal with standing waves is two-fold:
1) with your budget, room size, and desires in terms of seating area, you should definitely be considering multiple subwoofers. At least a pair. Although you might be a very good candidate for using four subwoofers.
2) Bass traps. These are passive room treatments. They're simply panels made of insulation. You first treat all of the vertical corners, followed by the upper perimeter of your room if necessary. Bass traps - and all acoustic absorption, for that matter - work by absorbing soundwaves. Normally, sound waves will travel outwards from your speakers and subwoofers. When those soundwaves reach a normal, flat wall, ceiling or the hard floor, they reflect off of such hard, flat surfaces. So you've got these soundwaves normally bouncing and reflecting all around your room. Especially bass soundwaves, which are very long and powerful. And sometimes, waves will "run into" each other and either "double up" or "cancel" each other out. A standing wave occurs between two parallel, flat surfaces when the soundwave is exactly the right length so that it perfectly doubles back on itself. So it keeps bouncing back and forth between those two parallel walls, and keeps doubling up and cancelling out in exactly the same spots, over and over. If you happen to be sitting right in one of those spots, you get a HUGE, way too loud note at that particular wavelength, or you get dead silence, no matter how loud the subwoofer or speaker is playing that note!
But if you use bass traps and absorption, now the soundwaves reach the wall, hit the bass trap or absorption panel instead of the hard, flat wall, and they get turned into harmless heat, rather than bouncing and reflecting all around the room

Now, you're hearing the sound that's coming directly from your speakers or subwoofers, rather than all of the reflected soundwaves. And those standing waves don't occur nearly as much, because every time the soundwave reaches a wall, it's being absorbed, rather than reflected back on itself.
So enclose the room!
Next, we've got to talk about that equipment closet. Few issues:
1) the way it's shown in the diagram, it blocks your walkways on that side of the room. Although, like you say, the seating might be different in the final layout.
2) Not a big deal at all, but it would take up one full corner, preventing you from putting bass traps or a subwoofer in that particular corner.
3) Having it in that location might make it difficult for you to access the back of your equipment, unless you use a fairly fancy and expensive rack that can pull out, and/or rotate.
Is there any way of moving your equipment into that area under your stairs? Or perhaps recessing the equipment rack, even partially, into that space under the stairs?
I'm guessing you might want to keep open access to a disc player or videogame systems or the like within the theater. Kind of a hassle if you have to go under the stairs every time you want to put in a different disc

But if you could make use of that area under the stairs, or simply have the access door for that area be inside the theater instead, you could hide your equipment in there, have much easier access to the back of all your equipment, have way more room for wires and cables and such, and still keep easy access for switching discs and whatnot. Just an idea, anyway
Then we've really gotta talk about where you're gonna put your seats, and exactly what the seating is going to be. Right now, the two rows are shown a little bit close together for my liking. I find 5.5 feet from the back of one row to the back of the other row to be about perfect. Right now, you're only showing about 4.5 feet, which could easily lead to someone in the back row kicking the head of the front row if they're fully reclined
As already mentioned, acoustically speaking, having your primary seat at about 1/3rd of the room's length (from front to back) is more or less ideal. You don't want it dead center. That's the worst spot, other than pushed right up against a wall.
So I'm really thinking with what you've said, AND because you've said you don't really care about 3D (which works out great, frankly

) you could have your eyes and ears at about 13-14 feet from the physical front wall of the theater room. That'll put the physical back wall about 7 feet behind your ears, which is a nice distance to have for ideal surround sound. This would pretty much make a 2nd row a no-go. But if you're really planning on just one row anyway, this would be ideal.
Keeping the false wall at the front with an acoustically transparent screen and the speakers behind that screen with about 2 feet to work with from the screen to the physical front wall is great! That'll give you an 11-12 foot viewing distance with this seating plan, which is a really nice distance in a home theater. 10 feet is a bit close in a theater this size. You'd sort of feel as though you're sitting on top of the screen!
I'm all for wanting to go BIG for the screen size. But you're going to want to consider how you'll handle 2.35:1 aspect ratio content vs. 16:9 aspect ratio content. It's easy enough to just use a very large 16:9 aspect ratio screen. But that will mean "black bars" above and below the image for 2.35:1 content. In a theater of this size and price range, it's usually nicer if your 2.35:1 aspect content has the "bigger" screen, the height always stays the same, and you simply close in the right and left sides of the screen for 16:9 aspect content.
This gets a bit tricky though - especially with an acoustically transparent screen. To start, motorized screen masking systems are not cheap! And the least expensive ones are not acoustically transparent, so now you'd have to make sure that your Front Left & Right speakers are within the borders of the 16:9 aspect screen. Otherwise, the masking, when closed, will block the sound. Acoustically transparent, motorized masking systems are prohibitively expensive. As in over half your budget all by themselves! So yeah, that's not gonna happen
Frankly, we need to talk more about this. I'm out of time right at this moment. But again, work big to small, anyway. We should sort out the exact layout of the room and the seating first. We'll worry about the screen after that.
Final question, the diagram shows the 1st row of seats on a elevated floor, and then the 2nd row on a riser above that. This is great for soundproofing if you are planning to use a floated floor in the entire room. But I was just curious where you got those plans.
I'm not sure where you're at in the construction phase. But if you're still able to make changes to the plans, there is a WHOLE lot to consider in terms of the construction - especially if you want to consider real soundproofing. And there's all the electrical and HVAC to consider as well. If having the room be dead silent to the rest of the house isn't really a concern, then normal construction is just fine. But those plans make me think that someone in your design and construction team was thinking about soundproofing. So it's worth my asking
