MaximumPC also ran a similar article.http://www.maximumpc.com/article/features/experiments_memory_ram_myths_put_test?page=0%2C0
You should at least read pages 2, 3, and 4. (Page 1 addresses DDR2 vs DDR3)
That should answer your questions.
I agree with halcyon. If 12 at 1600 doesn't work, then 6 at 1600 will be more than enough