You could save some $$ from getting a Da-Lite screen instead of a Stewart. As for a projector, an NEC XG-135LC or XG-110LC would be a good bet at the $3500-4500 price range. If you want a really big screen, though, you will have to go with a digital projector. A good recommendation there would be either the NEC HT1000 with the panamorph lens or a Sanyo PLV-70HT (not the 60HT).
Get an HTPC with an Immersive H3DII for a scaler and you are set.
Get an HTPC with an Immersive H3DII for a scaler and you are set.