After looking at your basement dimensions a little closer; that would be the best solution. You’d have close to 13’ in width (and believe me, you will want every bit of this).
If you can convince your bride to move the traffic pattern through the laundry area, I’d close that wall completely off to the HT area. I’d then build a wall between the opposite exterior wall and the stair header with a doorway to the HT room all the way against that far wall. You could then put seating at 12’ and 16’ and still have room for HT egress behind the last row.
I’d then look at a good long throw projector (Sanyo Z4 might be a good pick) and mount it as far away from the screen as I could without using the zoom. By doing this you would have the option to install an anamorphic lens as you learn more about this hobby and get up to speed on constant height systems like Randy has. (they are supper trick and you'll want one if you ever see one in action)
With the fronts and center speakers tucked away in their own area away from traffic and side viewing, tower speakers then look as if they belong there. The need for the wall mounted speakers from an appearance perspective becomes a mute point.
On a side note, if it isn’t too late, I’d strongly suggest you reconsider where you’re placing your laundry room. Unless you have a chute / bell waiter system, carrying clothes up/down steps will get very old. I know from personal experience. I have a five level home and carrying them damn bags / baskets of cloths up / down stairs every frigging day is a pain.
