[VIDEO]http://www.youtube.com/watch?v=dpWNjFPDtRY]YouTube - Number Eight ..::.. 8-String Bass (octave string)[/VIDEO]
I was just thinking one of these dropped down to B would sound absolutely monstrous paired up with a seven-string.
Doug Pinnick used a Hamer 12 string bass a lot on the earlier King's X stuff and yes it sounded massive. He biamped his rig if I recall correctly he used gutiar amps for the high end and bass amps for the low stuff. It effectively gave King's X another rhythm guitar player.