Worth upgrading from Ultra-90?

[Slartibartfast]

Hey all, I'm going to be switching to a new case in the next month or so, and was wondering if people generally thought it would be worth taking the time to upgrade my hsfs. I'm currently using 2 thermalright ultra 90's (dual socket 940 system). I don't oc, but my biggest motivation for changing the case is high temps. Lowest cpu temps I've seen are 47c idle. I know it's airflow, not hsf contact.

So basically I'm wondering if I would see much difference upping to something beefier, like the Zalman 9500, SI 120 or Scythe Ninja. I think weight might be a concern because it is dual socket.

Any/all input is appreciated