Then the only thing left to do is to adjust your image until you are happy with the prints. If you are lucky, the same adjustment may work on a group of images if they are all the same 'darkness' to which you object. The print is real, so you need to adjust until it matches what you see in the 'real world' with your eyes. Personally, I'd adjust my monitor until it matches your prints, so at least what you see on your monitor is what you will get out of your printer.
I hate to belabor this point, because you have made it quite clear that you are using a calibrated monitor. When I bought my HP 24" monitor I had to take the 'brightness' from 400 cd/m2 to 120 cd/m2 before it was fully calibrated. Colors were fine but brightness was crazy bright. My wife complains that the monitor is too dark. Oh well, that's the way it is, "use the laptop" is my response.