Motor head experts seem to say, you dont need em unless you do. Meaning, if your ignition has enough power to jump the gap as it is, there is no reason to run an ignition box. So unless youre having problems with misfiring, the extra voltage wont do anything for you.
Plus, it seems that the multiple spark discharge stops at 3K rpm, so the multi spark function is simply to improve low speed driving on high performance engines. Not make power.
http://speedtalk.com/forum/viewtopic.php?t=6616