In theory, cuts won't help the contrast in low light situations. The cuts are a carry over from service controls on analog CRTs. Their purpose is to rebalance the light output of the red green and blue channels so that the same gray color temperature can be maintained from 1% to 100% white.
On CRTs, the different color phosphors used might respond differently to the same voltages. So the voltages delivered for each color channel would need to be adjusted individually. The cuts were used to adjust the low light values, the drives for the medium and high light values.
These controls were carried over into LCD panels. The cuts and drives are used to balance the color channels for the same color temperature of white from 1% to 100%.
Do you have Dynamic Contrast engaged on the Advanced Picture Settings menu? Any setting but off, will crush blacks.
You will need a test disk to set brightness levels properly. For HDMI input on the two machines I have calibrated, the proper brightness settings were 58 and 57. That setting was way too bright for my friends DVD on component though. His component DVD brightness setting needed to be way lower at 28.
The Static Gamma adjustments have the greatest visible effect on the medium luminances. Lower numbers darken, higher numbers lighten the medium luminances. You should see only minor differences (if any) at the lowest and highest luminance levels.
If you have access to a Bluray or HD-DVD player, I highly recommend setting brightness and contrast with the AVS HD 709 test disk. http://www.avsforum.com/avs-vb/showthread.php?t=948496
The disk is a free download and has the best brightness pattern that I have seen.
For SD DVD players, I don't know of a free equivilant to AVS HD 709. There are commercial disks, DVE and Avia have several titles. Getgray is a downloadable DVD image after a 'donation' for the developer. Check out the Display Calibration forum for more specifics on those disks. I have both Avia and DVE disks, the brightness patterns on those disks are IMHO not as good as the AVS HD 709 disk.