As Jeff said, whites on a Greyhawk appear white, and I no longer feel that black level is an issue anymore after my recent visits to my local Warner cinema.
My Davis produces better blacks than I see there, and if we are reproducing the home cinema experience, then black level isn't really something to worry about.
Blacks on my pj appear pretty black to me anyway, and as it is relative, you'll probably find the same. It depend on how critical you are though.
You could do what I did and spend about £28 on a home made screen using wood bought from B&Q, and blackout cloth (white cloth one side, white rubber the other) from your local curtain shop. I have a DLP pj, with only 800 lumens, and the image is plenty bright enough using this material.
See my homepage for some pics of the screen. Images are from my old htpc using Mpact2 mobo with built in graphics and sound.
I'll try to do some newer pics as a comparison sometime soon.
HTH
Gary.
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