Sadly I can't recommend this as an iTunes visualizer, it doesn't matter what settings are used, SoftSkies tears into the processor. This is on a MacBook Pro, Core 2 Duo, even with the window set to the smallest size, standard cloud detail and one of the scenery images taking up half of the display, it still uses 90% + of the processor.

The great thing is that the Gold and Platinum purchased versions do come with SoftSkies V-Bar, this is a standalone desktop application that even on its most aggressive settings, takes no more than 20% of the processor. V-Bar has a few preferences that can be fiddled with, nowhere near as many as the visualizer though, but it does auto-hide on mouseover which is a neat little trick.

All said, it's well worth looking at and trying.