and if $150 is too rich, you can pick up a nice sheet of Formica for about $30 that works remarkably well... I did that a couple of years ago as a prototype, to get a feeling for what size of "real" screen I should buy, and the Formica has been working great ever since
You really need to choose the screen and projector together... if you have a "bright" projector you can go with a grey screen and get better contrast, especially if there is some ambient light in the HT, but if you have a relatively "dim" projector then you probably want to stay with a white screen. Put differently, if you can't fully control the ambient light then you should look at either (a) bright projector + grey screen, or (b) any projector + high gain screen accepting the narrower viewing angle. Just guessing from your original post that the room will be a dedicated HT that you can make as dark as you like, if so that gives you more options.
In theory the high gain screens (eg VUTEC SilverStar, Da-lite HiPower) are best in rooms where you can't completely control the ambient light, but I have to admit that the most impressive images I have seen so far came from high gain screens in a dark room (duh!, I guess ;)).
If I ever get around to buying a screen I would be tempted to try a high gain screen even if it's just for the punchy image, although you lose viewing angle with both. The SilverStar seemed to have a pretty good horizontal viewing angle, although I never quite figured out how that worked (high gain + wide viewing angle aren't supposed to go together, so presumably VUTEC has figured out how to combine a wide horizontal viewing angle with a narrow vertical, or sth like that).
