Is the monitor capable of showing everything, warts and all, contained on the software. How good is the steering logic in your surround sound processors, and so on and so forth. Having reference quality equipment may not be enough. Too many times is the answer. Great equipment can only create beautiful images when it is properly set-up.
Top rank calibrated monitors can accurately replicate colors as intended.
A calibration by a qualified technician is invariably necessary. Even the best equipment doesn't perform perfectly out of the box. With home theater projectors, slight convergence errors can make an image appear softer. More contrast than your equipment can handle can make a picture look soft or even distort the geometry. Too much brightness can make a picture look washed out.