Hi Julius,
How are you judging this, exactly?
What calibrator did you use for your old screen?
Is it an entirely new computer system, or have you only replaced the screen?
Even 600:1 is too high in my opinion. 400:1 is better.
Basically, the higher the contrast ratio, the further away from print matching you'll be. And I guess it goes without saying that print matching is the goal of calibration.
On that subject, which pro lab are your prints from? And how many prints do you have?
The purpose of calibration is to make your screen match your prints. It doesn't matter if you don't like the prints, your screen still has to match them. So if the blacks on screen are lighter than the blacks in print, you need to darken the blacks on screen.
However, I urge you to take your light into consideration. Have you read this?
I'm so sorry, I haven't used CN since version 4.