a few things to look for when purchasing.
ansi lumens of 2500 or better for bright settings.
get a projector of the same aspect ratio as your computer monitor if running from a pc(you can clone the 2 rather than having a stretched desktop)
if you get a projector with bad display(black/ white levels) you can adjust the gamma in your computer to get it right. if you are running a cable box or game console it will look like crap. my old acer and benq was this way. the dell however had a really good picture out of the box.

thrash;326293 wrote:
building a 4.5 ft tall, 8ft wide screen gives you a perfect 16x9.+1
My first screen was 120" diagonal built with 2x4s and cotton sheets. I built a new screen this winter - same dimentions as you, but I used a canvas stretcher frame and SMX material so I could place my speakers behind the screen. The canvas sretcher frame was really nice to work with - http://www.utrechtart.com/Best-Aluminum-Combination-Pro-Bar-Stretcher-Bar-MP26132-i1005668.utrecht. I used two cross braces to make sure it didn't pincushion in the middle. The next thing I want to do is add a maybe 1x2 frame around the whole thing covered in black velvet to get crispy edges and no bleed onto the wall behind.

The plasma honestly needs more natural light control because the glass is so glossy. The projector is MUCH sharper and has no fuzziness. If you get close enough there's a screen door effect. The plasma is running HDMI from an xbox 360 so I don't understand why I can perceive fuzziness/sparkling up close.

If you can control the light (which is easy in a basement), projector is absolutely the way to go. I built my screen out of 1x3 clear pine, and used some gate-straightening kits (the metal wires with turnbuckles) as diagonals to keep it square. I covered it with the black-out cloth (rubbery white stuff) that is sold at Jo-Ann fabric. It comes in 54" wide bolts and it is stretchy, so building a 4.5 ft tall, 8ft wide screen gives you a perfect 16x9.

I built a projector mount out of 1x2 scraps and sheet metal. I have a BenQ W500, which at the time was the most affordable 720p non-DLP unit. I run HDMI out on my media center PC and component video from my 360. Both look awesome. The projector is always shooting at its native resolution and the input devices both have excellent scalers. I don't recommend DLP projectors because the colorwheel in my old Infocus X1 was just too loud. Maybe other wheels are quieter, or maybe DLP is all the way obsolete now and nobody uses it. I haven't checked lately

The main point is that you can get a 100 inch picture with no distortion, no uneven light problems, no funny business -- and you can install it all by yourself (my screen weighs perhaps 20 lbs total), and the whole setup - PJ, screen, and mounting can be had for under $1k. And if newer PJ's come out that interest you (i may get a 1080p setup down the road), you can re-use your screen and mounts and be up and running in 5 minutes.

You mentioned entertaining - I've got 2 rows of seating, but unless there's something like a Vikings playoff game (yeah, right) on the screen everyone gathers around the bar. If I change anything about mine it'll be to have more area back there. Pool table, card table, and Wii all see some use too depending on the crowd.

I have 2 projectors and love em. My main projector is a Sony G70 CRT - only 1200 lumens but the black levels still can't be beat. It's set up with a 1.0 gain 110" acousically transparent screen. My second projector is a Vivitek H1080FD - for parties we set this up on 70" DIY rear projection screen by the card table, or on the 144" inflatable screen outside if the weather's nice enough. 1080p, but the picture quality isn't nearly as nice as the ol CRT.

Do a lot of research before picking a projector. Personally, I'd take contrast over brightness if a choice needs to be made. I recently recommended and helped install an Epson 8700UB in a friends house and it looks fantastic. Both my Vivitek and his Epson came from http://www.visualapex.com/ - very happy with their service. His Epson came with a universal remote, IR repeater, dust cover and extra lamp for $1800, but sadly it looks like that deals gone now...

Happy to help, let me know if you have any questions.