Use MSI After Burner to monitor and control fan speeds. From my experience After Burner does a better job than CCC does.
I would also recommend setting a fan profile to keep fan speed percentage in line with GPU temp.
I have owned two XFX 5770's. My first one lasted right at two years before it started to overheat really bad. The replacement has been better but appears to be slowly warming up. So by monitoring temps I know when I need to RMA this one.