A slightly different perspective. On the last 3, the clouds play a reasonably significant part of the image. Yes, a polarizing filter will help quite a bit here. However, you can also do a 3 shot bracket (camera can be setup automatically to do this), and then combine the three shots together with software - Autopano, Luminance HDR, and my favorite Oloneo PhotoEngine. This would probably bring the clouds out quite a bit. HDR (High Dynamic Range) can certainly be overdone and over used, however for very flat scenes like these it may help. Certainly something to experiment with to see if it has any appeal. Each of the software utilities have a free trial capability.