What is a good level to defeat the twin sisters in Portrait of Ruin

Well...I went up against the sisters as Level 60 or something, but that's because I was busy completeing quests and mastering most of Jonathan's sub-weapons. I think you should go up against Stella and Loretta as Level 45+, but only if you're trying to beat them. Remember-to get the best ending you will have to use Charlotte's Sanctuary spell to cure them.
If you want help on that, just ask or write someting on my message board.