Eu encontrei essa pergunta e resposta intimamente relacionada, embora não funcione para mim (estou executando o Windows 7 64 bits)
I think I just found the answer to my own question. Better solutions are welcome of course.
With the application Display Tuner I can set the brightness, contrast, color levels and speaker volume for my external monitor. Not the video card, my actual monitor. It allows me to set hotkeys for separate profiles, lives in the tray (notification area) and is free for non-commercial use. The main draw is that it only supports monitors that can be controlled through DDC.