According to Corsair George, whichever fan has the highest static pressure should be the push fan.
I was running an H70 for about 7 months and it never got any louder. I just removed it this week and it was working the same as the day I installed it. What type of noise is it? Have your temperatures changed?
The H60 is incrementally better, but it's more expensive too. The H50 is great and could likely do as good a job within a couple of degrees. Personally, I would go with which ever one you can get cheaper (likely the H50) so if you have an accident it won't cost as much. Although I do like the lower profile pumps of the newer coolers...
i saw the answer you gave to mergatroid; and i wonder how i can know wich fan has the highest static pressure??