If you are serious about DLP then you really need to go with the DreamVision unit. The DL-500 is an 800 x 600 unit (list $6495) and even on a 110" 16:9 screen with a Crystal Image scaler it's amazing. If you REALLY want the best DLP out there these days the next step is the DreamVision Movie Star Plus, 1024 x 768 and is in a league of it's own! :-) Of course the list there is $12,995.
The thing that seperates the DreamVision units from the rest is the three-part color wheel. While the rest are still messing with the r,g,b and translucent wheels, DreamVision has had a three part wheel for YEARS. This really affects the full-motion video more than you can imagine.
The only trick is the 17 degree offset lens, but it does have zero keystone error if you set it up right. On the downside there is no keystone error adjustment. :-( Although it's so light that once you measure the distance, you hang it, and it's done. The trick is to get it LEVEL! If you don't you'll have keystone error. As for figuring out where the screen will go... well... you can either put the screen where you want it then adjust the height of the unit, or put the unit up and adjust the height of the screen. Basically, you'll have about an 18" drop at 15' or so.
Tony / Premier AV