I had a similar problem a couple of years ago for the society I help with. We are using a Sony projector, and I think it is 1100 lumens. It works very well in a hall. The connection with PC is via standard monitor cable that is usually supplied with the projector. Beware the cost of replacement bulbs; this is not often quoted (PC ADviser does!). A comparison of Sony digital video projectors here click here may be of interest.