I've just downloaded your tgd and I did setup the following render settings:
Quality 0.8
AA 6
GI 2/3
Cloud and atmo settings were the same.
I also saw that you didn't alter the contrast and gamma settings under the "effects" tab of the renderer.
Increasing contrast to about 0.3 - 0.4 and decreasing gamma to about 1.5 - 1.9 will make the image very crisp and clear and also reveals a lot more details, in clouds for example.
Changing these settings heavily affect the overall look of the image so I left them untouched. If I have some time left I'll do a small test render to see how that works out.
I'm rendering it at 3 cores at once so it should be finished this afternoon I expect (it's 10:20 a.m. here now and after 23 minutes all 3 renders finished their GI pass).
I enjoy doing this because it's also a chance for me to see how my new system renders cloudscapes so I can estimate rendertimes better in the future

And oh yeah...render resolution is 1100x825.
I presume you want to post-proces your image, so where do you want me to send them to?
If possible I'd advice you to use the .exr file because this gives a lot of control in post proces on how the clouds look.
So I can send both bmp and exr version if you'd like.
Martin