As far as equipment I would suggest saving your pennies and ordering everything all at once. If you plan on sitting on the equipment over the next few months it makes more sense to buy it when you need it rather than have it sitting around and using up the warranty.
AVS is a great place to get a projector. B-Stock units are a great buy and come with full warranties. So many options on the screen. I tried out seven different samples, from five different companies. The Elite screen was by far the least expensive and looked good, but there were a couple of things that it didn't do well with in my room.
Not sure what the rules are on posting links to places to buy equipment but there is one place that sells referb Onkyo and Denon AVR's. Could save some cash buying a refurb and put the savings towards something else. Whichever you choose make sure it has pre-outs for an external amp should you choose to go that route. I'm using an Onkyo 808, with an external amp running my L-C-R, and the AVR powering my surrounds. I'm very happy with this setup.
Seating could be a couple of couches for now. Personally I would worry about seats later and concentrate on purchasing the equipment you want. Better off buying a nice projector and screen, than skimping on those two items in favor of nicer seats.
Everything is looking great so far. You're a lot farther in your build than I am....