From the time of X3, the color management has been revamped. This shows up in X6 as a completely different management settings user interface. The current (X6) color management is more correct than that of X3. And as such, CMYK design is CMYK being sent to the printer driver. The printer driver, as I noted earlier, is trying to translate the CMYK values as incoming RGB values, into CMYK values. Or, in other words, (in near technical terms ,) the colors are being screwed up royally.
For a test, do a simple design in CMYK and print it then change all the colors to RGB and print that. See which print comes out closer to what you see on the screen.
If you have a 4 color press, then by all means, do output the CMYK design to it, as you should also have a (CMYK) color profile for that particular press with its set of inks. But if your printer is an office printer, connected to your PC or you local network, then it probably understands only RGB for color input and if you feed it anything else, then it will mis-interpret the colors and you get off-color results.
Do post a screen capture of your color management settings here, so that we could see if you have something mis-configured.