A good ventilation is very important. I think that the temperature will decrease many degrees after that. To change the cabinet is a good idea.
Anyway, although the cabinet you choose is a good one, I would choose the Cooler Master 690 II Advance. It´s the new version of the 690.
Here you have a video review: http://www.youtube.com/watch?v=Ed4RC6r2NTk
And if it´s not enough, you can change the heatsink for another better (Prolimatech megahalems or Noctua d14), but I think that you will get what you want with the new cabinet. The first step is that.