I just recently got back into this game to finish off the achievements, and I found a little bonus I figured I would share with everyone.
Note: For this you will have to have cleared up to level 19 on Heaven or Hell, and know how to make the dice land on the number you want. The trick with the dice game is to hit it when the top face is the number you want, it might seem to move fast for some people so it takes some timing and knowing the order of the numbers.
Now I noticed that level 19 on Heaven or Hell is a hundred times better to farm red orbs/proud souls on. First, if you know how to get the dice to land on the number you want, it just takes one roll to pass each of the floors. Second, seeing how everything dies in one shot from Blue Rose, you can clear this stage in literally two and a half minutes. The ending total for red orbs is around 9k per run, and you get 1700 proud souls at the end of the level. It is much, much faster than farming mission 7 if you need cash.