I have the 725HD. Did a movie last week on a 165" muslin screen and was very happy with the results. Got many comments on PQ. I was using the 720HD previously and the extra 1200 Lumens really makes a difference (same resolution and similar contrast). I was actually able to start cartoons while the sun was still above the horizon and it was a bit washed out, but you could see them. As soon as the sun was down, the picture was bright and clear.
I use a 32 watt amp w/ a pair of 6" bookshelf speakers and an 80 watt pwrd sub and have plenty of headroom.
There's just something about the big screen outside that makes any movie better.