My HT is almost the same size. I went with Quietrock in order to save precious inches on the sides, and am glad I did because it is tight with 4 Berks. I don't often have squeez back behind the seats, but when I do every inch counts, and they are not particularly stable so crawling over them could be interesting.
You may be more upscale than me on the audio, but I went with a 7.1 system (actually wired for 7.2, but that seems overkill). For the front 3 I used the Axiom M22s (bookshelf speakers). I had planned on using towers but the Axiom guy talked me out of it. The sound is great and that may be an alternative to low profile speakers. The axiom guy also tried to talk me into just a 5.1 system given the size of the room, but I did not listen.
I also went with a square stage with an arc extending out on the bottom level of the stage. I think it makes the small space look more flashy, in a good way. I had planned on a matching arc on the ceiling, but ended up scrapping that idea because I was worried about making the ceiling look too low visually. I ended up with a tray ceiling in the middle of the room due to some miscommunication with the contractor who was renovating my basement, but I like the tray ceiling and in retrospect would have liked the ceiling arch -- I have three spots along there now, so I won't be doing any retrofitting.
My screen is a 50" high 2.37 CIH. I had an anamorphic lens but because of the screen size and short throw, the throw ratio was too low to use the lens, so I sold it and now zoom. My miscalc was due to using 1.78 numbers when determining the ratio, and you are too smart to do that, but still beware the small ratio.
If the door placement requires a smaller screen than you want, perhaps you could put the screen on a slide rail so that you can move it to the side when you need to enter/exit the room. Then your stage and screen would be centered across the room during viewing.
If your target date is 2009, then you still should finish ahead of Logan. I sub'd too much out to qualify as a DIY, so I just don't feel right about calling him my beeyatch, but I am happy to watch you do it.