ok..my room is 21'by14' in my basement and I have decided on the Optoma HD70 front projector or the Mitsubishi that is in that same price range. I am wondering what size screen would be the best....I want to have 2 rows of 3 seats at one end of room, so the closest person should be about 15 feet or so away, I want the biggest screen possible...........also just one more thing, my dvd player currently consist of an Xbox..not the 360 but the original one, do I need to upgrade that for better picture ??

Get the biggest screen that will fit in your room. I have a 92" screen, and although it would be great to go bigger, my room dictated the size. If I were to get anything bigger, I would have to switch from towers to bookshelves and put them below the screen. Or I would have to buy a perforated screen, build a faux wall, and put the speakers behind the screen.

Definitely look for a better DVD player. The xbox is not the best dvd player. I noticed a HUGE difference between my 360 (upgraded dvd player from the original xbox) and my cheapy samsung player.

That said, go for something nice like an Oppo. It upscales the video from 480p (standard def) up to 1080p (high def). You can pick up the DV-981HD (http://www.oppodigital.com/dv981hd/dv981hd_index.html) for $229.