Are you guys sure the HTPC sharpness issue is inherent to the projector?
I am not questioning anyone's findings, I am just a little confused that Benq would have this issue since I have never seen, nor heard of this issue on other Benqs. When I say not seen it, I mean it can be there until you fiddle with the settings of the HTPC and projector and get it matched up. I think on the Acer we are sure the problem is there, but I didn't know the Benq would do it.
It almost sounds like resolution or aspect ratio confusion, this is not an uncommon problem and not necessarily the projector. For instance, on some DLP's I have owned, setting the aspect to 16:9 (even though the video card is set to output 16:9) does not work. What happens is the projector misinterprets the signal as being smaller than it really is and it blows it up around 5% to 10% into a re-scale, or sometimes it can do it more severely or even be completely confused. For my Pro8200 DLP, I have to set it to 16:9 for a bluray player, but must change back to AUTO for the PC. Only in AUTO aspect mode does it not cause scaling and does it properly interpret the size of the display, and it doesn't matter what I have overscan set to, it will do it regardless.
I would play around in the HTPC video control panel's scaling settings for the video card itself, as well as the projector's aspect ratio options and see if any combination produces any results that are better. It may take several different combos to find one that works. Then I'd try different PC's and remove any receivers or HDMI switches from the equation.