In my first two rented apartments, my only display was a 92" High Power Model C Da-Lite manual pull-down screen with a Sanyo PLV-Z2 720p LCD projector. Being that it was my only display, I had thick curtains over all of the windows in my living room/dining/kitchen area
You can get away with a little bit of light - but not much. The High Power screen certainly helps because it is retro-reflective - which means that it bounces light back to its source rather than "spreading out" the light that hits it. With the High Power, much of the ambient light is reflected away from your eyes and back to where it came from. At the same time, if you position the projector close to your eye level (like on a shelf directly behind you or on top of a coffee table in front of you), the light from the projector is bounced back along the same path, which basically directs it right into your eyes. The retro-reflective High Power screen is also very high gain, so it looks way brighter than most typical screens. The High Power is a much better solution if you have a bit of ambient light than a "grey" screen, IMO.
With the shades that you have right now, there is no way that a front projection setup would look truly "good" during the day though. At night, I think a front projector setup would look good in your room, but during the day, too much light would come through those shades. I got tired of having to keep whole apartment dark just to watch TV during the day
So you would either need to get some genuine black out curtains and keep the entire room area dark, or else you would want to have the plasma for daytime viewing and parties with the lights on and then have the front projection setup for night time movie viewing.
Your room is never going to be pitch black. So I honestly wouldn't bother looking for screens other than the High Power. As jostenmeat explained, it hides waves very well. So you can " get away" with a much less expensive manual pull-down High Power screen and I honestly think it would be the best choice for your room regardless.
I'm in total agreement with jostenmeat here - I think your best setup would be to have the plasma. If you want to add the pull-down High Power screen and a nice projector, there's nothing like a truly huge screen for movies! But the plasma should be your first priority, IMO. You'll be able to use it during the day without altering your current room. You'll be able to use it during parties with the lights on. And it's a better solution for "casual" viewing too, IMO.
So I'd suggest that you get the plasma first, but keep the front projection setup in mind. I wouldn't really suggest having the front projector as your only display in that room. I've lived through that and it's darn cool at first, but it also has its downsides