If you've gone through the slew of information over at
www.projectorcentral.com then you already have a good deal of quality info at your hands.
IMO - I would be hard pressed to get any DLP priced over $1K more than the Z4 or AE900. The benefit simply isn't there with DLP anymore. It used to be plain and simple - DLP was much better than LCD and LCD didn't compete.
Now, LCD competes, costs half as much, includes lens shift and zoom that blows DLP away, and still has the great color that LCD is known for. Is the H78 perhaps a bit better? Yes, I think it is, maybe, a bit better.
I might go so far as to spend... maybe... $1,000 more for it. But, not one penny more. Really - it is not THAT much better.
In 1-2 years we will also be looking at 1080p resolution I believe on a lot of front projectors. Those may very well be at the $4K -> $6K level that the H78/79 are at right now. We will either see the 720p projectors disappear altogether or they will drop to $2K and actually, finally, go head-to-head with LCD.
Right now though? When price is included in the overall value, LCD is kicking the big ol' turds out of DLP and DLP is being way to slow to throw a counterpunch.
As for your screen? I think Carada is a very excellent value for the money and everything I have heard from users seems to be favorable. I strongly recommend them as a great value for your cash.