Assuming you don't have a LUT box, or a display with LUT capabilities, something I've not seen discussed on the forum (which might provide a clue to an answer), is: is there any place for video card control adjustments in calibration? On my nVIDIA Quadro 4000 control panel, I find settings that will allow me to adjust the Brightness, Contrast, Gamma, per RGB channel, as well as Digital Vibrance and Hue. Or, you can choose to let 'Other applications control color settings'. This can be done for desktop color settings as well as for video color settings (although I'm not yet sure of the difference for a single screen - e.g., if there is a video playing in a window on a larger screen).
I've been unable, through auto calibration and display controls to get my second GUI monitor (lower end Dell) to even remotely resemble my higher end Dell main monitor (U3011). However, I was just able, with a slight adjustment to Gamma and Contrast have the GUI monitor visually identical to the other. Before, it was too bright, even though OSD controls were adjusted, and the blacks were greatly elevated. It looks very good now.
I don't expect it to be color accurate at this point, but it did get me very close (visually) to the other one which makes my eyes happy. Is there a roll for these on-board controls (since I assume they affect everything coming from the PC, like a LUT box, without the color correction, of course)?