G-Force is soft and isn't exactly...involved.
Try
Fielder.
(40KB download, about 15 seconds with 28.8K)
My instructions:
(1) Install the plug-in at:
[user]/Library/iTunes/"iTunes Plug-ins"
(2) Restart iTunes.
(3) Turn off full screen res.
(4) Turn on fielder visuals.
(5) Go into Options.
(6) Click on Erase Vectors, uncheck Vertically Place Vectors, and set the frame rate to 1.
Here's how this works. The bars in the visual move from one side to the other, depending on the song. The left side of the visual corresponds to your left ear. The right side corresponds to your right ear. The position of the bars indicates where inside your brain you feel the most intense sound.
BTW: This was mentioned in the July issue of MacAddict, with 100 freebie apps.
Check it out. It's not what you would expect, but it's appealing.