Seriously speaking, you should just get the 5Dmk2. If you even think about it, it means you are not satisfied with what you have now (the 50D).
And please do not get annoyed by the other posters here. You only have yourself to blame, by not being specific, and not providing some background info that would help others help you. Look, it took you till post 11 in this thread for you to list what camera you have and how you use your camera and what subjects you usually shoot. We can't read your mind dude.