Reduce iWow for iTunes' CPU usage on slower Macs: "I've been using iWow for iTunes some time now. It makes my music sound great, but there is a downside to it ... if you have a 'slow' Mac like mine (mini 1.42 GHz), it eats up to 42% of the CPU. During CPU intensive tasks, that can be a real pain.
After adjusting some settings, I've come up with a way to reduce the CPU usage significantly! Adjust the settings to look like the ones in this image, and make sure you save those settings.
After these adjustments, disable iTunes' built-in equalizer. After switching to these settings, my CPU usage with iWow dropped down to around 9%. Good luck!
Mac OS X Hints - http://www.macosxhints.com