When has a digital projector ever looked brighter or better than an analog projection? IMHO, never. Not to mention, once you find the suitable analog projector, you could probably buy two and do a stereo slide show before you could afford one digital projector. But I digress....

There are always some long throw lenses on eBay, specifically I remember seeing some Buhl ones. I'm sure they're now selling for a fraction of what they cost new. I'm sure resources abound with regards to high-power projectors, etc. Make sure you have backup slides and an excellent cooling system.

Long throw simply equals long focal length I believe.