I recommend you wait 45 more days until after CEDIA to see what is new. There are several new models coming out, at least one from Mits and one from Benq I believe.
I believe the sp891 is more of a crossover projector and only has a 3x color wheel, so I recommend the Benq w6000 paired with either a High Power screen or a Gray screen. If you don't want to replace the screen, all I would say is that adding tons more brightness will not totally overcome your ambient light issue. It might help, but there isn't many home theater projectors that much brighter than the Benq w6000 anyhow around its same price.
If you wanted to spend more, take a look at the Infocus sp8602 as well, it produces a brighter best mode than the Benq.
Keep in mind that the Benq w6000's lens shift makes it so that the projector has to be placed 1/8 screen height above or below the bottom and top of the screen. This can make the Benq difficult for certain ceiling mount jobs, but it depends on ceiling height and what not, so just check that its lens shift works for you.
There is the LG cf181d, but I'm not a huge fan of it, but it isn't bad.