I saw in Harvey Norman the other day, the Panasonic AR 1000 for about $2k, this is a full HD "power house" of a projector with lumens to burn. this would leave you about $3k for screen (under $500) and AV amp/speaker package ($2.5k). This will get you some fairly decent gear.
Have you seen the optoma or just going from reviews?
I only ask as the Optoma is a DLP projector which some people (myself included) find irritating to watch with rainbow effect and other visual problems. Just something to be aware of.