Just wanted to update this thread since things appear to be primed to start moving. Here's where we are.
Home theater area in the basement has been mostly cleared of stuff, and I'll be taking a new set of pictures to show the empty space that we will be excavating, refinishing, and building in. I have a contractor lined up to excavate, and since I'm doing all the work to get some ceiling height, it made sense to go ahead and do some additional under slab plumbing and add a 3/4 bath under the stairs. Now have a basic plan from Dennis that shows the home theater, kitchenette, as well as that bath, and am getting the drawings from the structural engineer so I can get the permit and start digging.
Law of unintended consequences says there are always unexpected expenses, and that's held true so far. Beyond the need to move some plumbing (to get it out of the way of the viewing pit), and the opportunity to put in the 3/4 bath, it turns out it's cheaper for me to actually retain the excavated soil on site versus trucking it away. And if I'm going to do that right, I need to build out some retaining walls and terraces in my hilly/downslope backyard to hold it all. The bonus is that I get a nicely redone backyard with planters, but that's another 10k or so that I wasn't expecting.
Here's the current plan. For some reason, I can't upload a PDF to AVS, so you'll have to live with the jpg.
Will post pre-excavation shots in the coming week, and then document as we start going through the process. Finally moving ahead!