My point was never about the CRT, but whether the upgrade does indeed deliver the 256 shade of gray they promise or not. For example, the 540c LCD does not even come close to providing 64 shades of gray, its more like 25.

Seems like it would be worthwhile to stick one of those new SVGA 9" grayscale tubes from ebay in there, you'd probably get a better picture than using the standard tube that apple sticks in there since an SVGA tube would have a better dot pitch, etc... not to mention all the use and abuse the original tube has seen after all these years.