And so you know, that card is a light-weight. Should be just fine for Diablo (It ain't Crysis). I also recommend getting Ati Tray Tools (DO NOT RUN WITH CATALYST CONTROL CENTER AT THE SAME TIME), so you can fit in a few more performance tweaks/
I think it will run. You have above average settings and should be no problem really. Even, I think you will be able to run on the highest settings easily. Btw if anyone of you diablo fans is interested, you can check out all diablo books that have come out so far http://diablo3guideinferno.com/diablo-3-books/ , those are really good and provde alot of information for new and old players.