I can't speak for the audio portion, but as for the video part: Plasmas have better color reproduction than LCD's. DLP's aren't bad, but are better suited to projectors than flat screens; still haven't seen a flat screen DLP that's really good IMHO. The Samsung line of Plasmas make good black levels which is important to the overall picture quality. Projection is a great alternative, but keep in mind ceiling height, throw distance (don't want your heads in the image) and the surface you're projecting on makes a HUGE difference as to it's construction and reflective values. Paint the wall, roll down screen etc. are different options.
If you're using the room width-wise, go with the biggest plasma that fits your budget. If you go length-wise, projection will get you a bigger image. Each option has it's downfalls.
If you want to make an image 105 foot by 139 foot I can help you there too as we do it often, but that would involve a little more remodeling!
