Hella's are hella awesome! That being said I pulled some FIAM horns off a box van at PAP and soldered them into my last rs. They were louder than the supertones I have heard.
youtube? it's a rather new site that host videos of all sorts of stuff. found it using a search engine called chrome
or maybe he didn't find anything noteworthy, like a review with multiple horns, or video uploaded by manufacturers...