I like two subs, as a very solid start. And an AT screen and AT wall pair up nicely with DIY subs, with simple black finishes.
Sight lines can be planned out by drawing the room from the side, and utilizing projectorcentral.com's calculator for projector specifications.
Assuming a 3.5" riser and a second one, isn't planning. You need a scale drawing with eyes, heads, and ideally ears, planted in space.
I often wonder if something like these chairs, might make for a decent front row, for a lower ceiling room. A little low to get down into, and out of, but they might be the difference maker in some rooms, so the second row can properly see the bottom of the screen.