Projector, screen and receiver (or separates). There will be other expense as my new construction moves along, but I need to get a handle on these three.
Projector: JVC HD250 or RS40. The RS40 is about to come to market and is one of the new 3D capable models. I might wait for the first review to see if it is better than the HD250, but realistically, JVC has simply put out more reliable and better overall product than about anyone else. Most notably, Sony who is the other competitor with LCoS technology. The Epson and Panasonic models (8700UB, and AE4000 respectively) are very good - but don't quite measure up.
Screen: If you actually have light control and do NOT want to go with making your own screen, then I do recommend the Carada Criterion in Brilliant White which is simply the best screen I've ever put together, except for Stewart screens at 3+ times the cost. Do-it-yourself solutions can be excellent but typically have some significant drawbacks, mostly related to how much time you have to put into them. That is, you can spend 10 or more hours properly building a DIY screen with a nice black velvet frame and with perfectly smooth drywall, or a well supported frame... but that time may not be something you want to give up. Still, I've built a 100" screen before (about 10 hours!) and it turned out beautifully for under $200 total in materials.
Receiver: I'll leave this one alone except to say that the Emotiva products really peak my curiousity. Denon makes some fine gear (PM me if interested). The Emotiva stuff is the way things are going and the ability to go with a separate pre-pro and amplifiers allows you to really go where you want later down the road should you upgrade.
All of this will run well under $10,000 pretty easily, unless you have it professionally installed and add a GOOD universal remote to the mix. I always put Crestron remotes in with my client's stuff because they always work and never leave people confused. But, this would be up to you as to how easy you want it to work for everyone in your home.
This will be a room within a room with a 15.5W by 21 or 22 ft long area. I believe I will devote 14x21 to the HT, and 7x21 to a raised area in back. I will have controlled lighting and black out windows and doors, but I will also want to watch TV and sports with the back zone of lights on.
Zoning lighting is crazy important! Also - complete light control means dark walls, ceiling, and carpet. Don't just put shades up - you MUST have everything dark for best control
Which brings us BACK to lighting! There is no such thing as to many lights. If you want it dark, turn 1,000 lights off, and it is just as dark as turning off 2 lights. Turn those 2 lights on and you can't see a thing, turn the 1,000 lights on and it is like being outside - in the desert. I typically would recommend a light about every 5 feet across a ceiling. Broken into no less than 3 zones. The first zone for 'general' room lighting where people are not sitting. One zone over the first row of seating, one zone over the second row of seating.
GET A REMOTE CONTROLLED DIMMER! Lutron Grafik Eye is a great product for this.
Seating distance will be about 12-13 feet, throw distance wherever it needs to be. 7.2 surround. General TV 40%, Movies 30% Sports 20% Music/gaming 10%. Don't need 3d. Don't know enough to evaluate screen size

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Screen width generally is .66 times your viewing distance. So, from 12 feet an 8 foot wide screen is THX specifications, and that's a 110" diagonal.
Receiver/separates need to be able to supply 2-3 zones and at least six additional speakers throughout house.
This all starts getting cumbersome. A second zone of audio can provide multiple rooms with the same feed just fine. Another amplifier and a speaker selector and volume controls in each room can do this. But, how far you take it is up to you and can incredibly impact budget. Since I have HDTVs througout my home, I put all my gear in a rack in the basement and distribute HDTV everywhere. It is very time consuming, and very expensive, and I don't use speaker selectors or zone 2 on my receiver. I use matrix switches and multi-zone preamps. As I said, this can get pricey depending on how smooth you want it to run.
Also will be piping sat TV to about seven televisions throughout house, but not final on how this is all going to work. I plan on using a Control4 system.
Even on the cheap side, if you are piping HDTV throughout your home, it will be pricey. I typically use Crestron and am less familiar with Control4. Other than saying that I get most of my Crestron gear used, so it comes in at about half (or less) of what new gear would cost from them. It works out really nicely for most customers.