I was thinking about this a while back. You could capture the menu sound themes from GT3 and use them. The only problem would be that they would be reloading everytime someone loaded a new page. That would cause the members to have strange breaks in the music. Which isn't too unusual - I fly through the menus in GT3 so fast that sometimes the songs only get a few beats out before I've moved on to something else. And you could use the sound effects from the game as 'onclick' actions.
But once again, sounds can be irritating if done inproperly. And as always, everything should be an option to the user (:
~LoudMusic