From the description, I'm not sure I quite understand what your problem really is, but if it is mainly about differences of perceived brightness between what you see on the monitor before softproofing (brighter) and what you see on the monitor after soft-proofing (duller) with "Simulate paper White" active , that is quite possibly normal and what you want - the soft proof is trying to mimic what the print will look like, and prints, especially matte ones, seen with reflected light will generally look duller than the monitor image, even with a good soft proof. Monitor light is direct transmitted light. You should make your final luminosity adjustments with the SoftProof active to get a print with the expected luminosity. What aggrvates this problem, especially if you are using an LCD, is that many people have their monitor brightness set much too high relative to what you would see on a print under normal viewing conditions. Turn the monitor brightness down to about 100 cd, recalibrate it and see whether that helps. The key thing you want to be sure of is that the soft-proof and the print look as close as possible alike allowing for some inherent difference due to the different kinds of lighting between monitors and prints. Also, the light under which you view the print makes a big difference. Ideally you want to be seeing the prints under Solux D-50 illumination. Hope this helps.
