Gosh, one thing you're gonna have to investigate is how much light you're really going to have falling on the screen. 20 foot throw distances are at the further limit of capability for units designed for home use. Unfortunately light is an inverse square thing, so the further you are sending the light, the more it disperses - and quickly.
The other, consequent problem can be addressed, albeit usually at some expense. Namely, the longer the throw distance, the more area the image occupies - and therefore, the more that has to be lit up. You can get a special long-throw lens for some (most?) projectors, but they aren't cheap and are only rarely included in used projectors.
Because of these considerations, I'd steer you away from CRT units, since they have the least light to begin with. The LCD units conversely appear to have the greatest net light output; they tend to be a bit newer also, and therefore long-throw lenses are somewhat less nearly impossible to locate for a used unit. (GOt that torturous english? :)
Actually, in a loft, you might actually prefer to use a unit that was really designed for the commercial business presentation marketplace. These tend to be a little noisier, have longer throw lenses, and sometimes don't handle motion nearly as well. But some of them are pretty darn good, and they may fit your particulars better than many of the more conventional choices.
I'd also carefully consider your screen options. They can help make up for light deficits in some cases, as they can be obtained with "gain" of up to 1.3x or even 1.5x. The gain is produced by narrowing viewing angle, so it's not a free lunch - but again, your situation may call for it.
I can imagine the kind of issues you may have finding speakers that fill your space! You have 7x as much volume as I do!!!
The other, consequent problem can be addressed, albeit usually at some expense. Namely, the longer the throw distance, the more area the image occupies - and therefore, the more that has to be lit up. You can get a special long-throw lens for some (most?) projectors, but they aren't cheap and are only rarely included in used projectors.
Because of these considerations, I'd steer you away from CRT units, since they have the least light to begin with. The LCD units conversely appear to have the greatest net light output; they tend to be a bit newer also, and therefore long-throw lenses are somewhat less nearly impossible to locate for a used unit. (GOt that torturous english? :)
Actually, in a loft, you might actually prefer to use a unit that was really designed for the commercial business presentation marketplace. These tend to be a little noisier, have longer throw lenses, and sometimes don't handle motion nearly as well. But some of them are pretty darn good, and they may fit your particulars better than many of the more conventional choices.
I'd also carefully consider your screen options. They can help make up for light deficits in some cases, as they can be obtained with "gain" of up to 1.3x or even 1.5x. The gain is produced by narrowing viewing angle, so it's not a free lunch - but again, your situation may call for it.
I can imagine the kind of issues you may have finding speakers that fill your space! You have 7x as much volume as I do!!!