hey sorry I didnt see this forum, I bought Infocus X1 and its same as Infocus SP4805, but only difference is that it has a different firmware, which means different default settings.
Another mail difference is that 4805 supports component video where as in X1 you have to get it done thru' an adaptor (which I bought for $20)
X1 is $800 and SP4805 is close to 1100.
NOTE: X1 is not manufactured anymore and you would be lucky to get one.
Dont get X2. Its NOT X1 + 1, but X1 - 1, meaning less feature than X1.
Also visit this page
http://www.projectorcentral.com/
The basic differences in "general" are that certain office product projectors are tuned for high lumens (1100) and home product projectors are tuned for low lumens (700-800).
Also office projectors are more reliable and less priced than home product projectors.
Last but not least, you will NOT find a retailer who sells both (per some agreement!) so you can not compare prices between office projector and home projector by the same retailer.
FYI, I bought my projector from
http://www.costcentral.com. I ordered on Thursday and got them by Friday. I dont know if they live near my place, but they do ship very fast.
FYI, I paied $165 for my screen seperately and bought ceiling mount for about $150. Once you buy your projector, give a call to mountsanmore and explain your hall and other situation (their website itsel has recommended screen etc but call them and they will guide you thru the material you should buy etc).
http://www.mountsandmore.com. You dont have to buy from them, but they are cheaper and I bought from them as well.