You're pea green with envy. You just visited friends who have put in a media room the kind with a projector hanging from the ceiling, a screen on the wall and surround sound. Very impressive. It's like having a movie theater at home.

So, you're wondering what it would take to create such a media room at your house. What's involved? What should you look for? How much will it cost?

While the projector is your primary concern, you also need to bone up on screens, bulbs, room sizes and audio systems.

There are many different models of projectors, says Gary Mack, electronics specialist at Larson's Home Furnishings in Medford. Prices and capabilities vary widely. The projector takes the place of a television set and just about any video source cable, satellite, etc. can be routed through it. Some people use large scale projectors only for watching DVDs or special events like the Super Bowl, while in other homes they actually replace the TV set.

And most experts agree that the equipment has improved a lot in recent years and come down in price.

"You want to get the highest lumens and contrast you can," advises Michael Johnson of Jacksonville, who recently bought a system and installed it himself.

You should have at least 1,000 lumens, better still in the 1,500 to 2,000 range, says Dennis Lane, president of Accurate Electronic Interiors of Medford. Besides brightness, consider the projector's resolution and contrast, adds Brian Pahl of Rogue Technology Solutions (formerly Quality Systems Integration, Inc.). Both firms design and install home theaters.

Most projectors hang from the ceiling, but desk-top and wall-mount models are also available.

Bulbs last anywhere from 1,500 to 4,000 hours before needing to be replaced.

Two varieties of screens on the market are solid and perforated. Lane notes that with a perforated screen you can place the speakers behind the screen instead of below it, so the sound appears to come directly from the picture.

Room size and design also play an important role, as do acoustics. Pay attention to room dimension ratios, advises Lane. If your room is square, or has a length that is exactly twice its width or height, your audio quality can be adversely affected because of the way the sound bounces around. Lane recommends a room ratio of 2.4 in length, 1.1 in width and 1.0 in height.

"You also want to make sure your home theater room has some sound absorbing properties," he adds. For example, don't put in a hardwood floor.

"You need to be able to make the room dark," adds Pahl. Many projectors don't create an image bright enough to be enjoyed in daylight.

How big should the room be? At least 18 feet long, Johnson suggests, and seating should be 10 to 20 feet from the screen, says Pahl, so the room should be large enough to accommodate that.

So what's all this going to cost? Depends on how far you want to go with it. Mack says what he calls "entry-level" projectors run in the $1,500 to $2,000 range. More sophisticated units can cost up to $10,000. Pahl believes "really good ones" can be found in the $3,000 to $5,000 range. Lane cautions against buying too cheap a projector. "Some of them have loud fans."

Screens run anywhere from $100 to $1,500, and bulbs $300 to $400.

At the high end, a fine home theater with projector, screen, bulb, speakers, and theater seating can cost $25,000 or more, says Lane. His firm designed one for a local home that cost $150,000.