The Superflash is a bright rear light if viewed from directly behind, problem is that once you go off center the light becomes increasing dimmer to almost non-noticable from the side. The Cateye 1000 solves that problem but it eats batteries fairly quickly and is pricey. I own the Cateye LD600 and mounted it vertically; this light is very bright not only from the rear, but even to the side; this light cost only about $15 and I have mounted 3 on my bike to form a triangle. A triangle of light is more noticable then one single light, thus for about $45 you would be very will lit up from behind as well as from the sides.
Also bar end lights are pretty decent as well, they give off some side light as well. Combined the bar with the rears and you would be extremily noticable. In fact I bet you that if you looked around at other cyclists in your area at night you will find that most have no rear lights and the few that do have a single dim cheap $3 blinky; thus you would be the brightest on the road.