Do not be fooled by the name. The SP4800 is the same exact projector as the X1. Infocus marketed the projector to the home theater crowd under the screenplay name, and to the business crowd under the X1 name. Then low-end business projectors forced Infocus to cut prices on the x1, but not the 4800. The two are as alike as the camero and the firebird - same exact thing but with a different name. If you want a 4800, you can save a couple hundred dollars by getting an x1- if you can still find one. The stores that still have x1's are probably down to their demo models and open-box-specials by now. Personally I have an x1 and am very happy with it.
For movies, the 4805 is a major upgrade. It has a brighter lamp (I believe 200 watts instead of 150), a 6-segment 4X color wheel (much less rainbow effect and eyestrain),and a native 16:9 resolution. This reslution has a few advantages ove the x1. For widescreen movies, the entire lamp is utilized- on a 4:3 model, the portion of light that falls on the unused pixels is wasted- making the picture dimmer. There are no "lightspilled" black bars(although that never bothered me), and finally, the 4805 can show widescreen movies with no resizing. There is a 1 to 1 mapping of pixels. With the x1, a picture that is 480 pixels high has to be either chopped a little at the sides (in overscan mode) or squished down to 450 pixels high. This resizing can cause some distortion.
The x1/4800 has one major advantage- if you can still find an x1, it will be cheap. (almost half the price of the 4805- I don't think I'm allowed to name prices). If you have to go up over a grand, though, you might as well get the 4805.
Avoid the x1a- It is a pointlessly stripped-down downgrade from the x1. X2 although brighter than the x1, is also a downgrade in many ways.
