The only thing I did not follow the instructions on was pointing the Zalman to the rear of the case and instead pointed it up...I thought it would make most sense seeing that the case has a fan right above it blowing out and heat rises.
I have Antec 900 cases. I do the same thing. I figure that warm air wants to rise. Why fight physics.
Idle temps seem a little high. What are your load temps?
Also, download RealTemp and use it for a second opinion.
And make sure that your HSF is properly installed.