If you already have a Magicshine headlight, then their tail-light is the way to go. For $30, it is brighter than anything else in that price-range. If you need a better headlight as well, consider buying Geoman's Commuter 900 pack, which includes a headlight, tail-light, battery pack, connector cables and O-rings, and a battery -- all for $120.
I have used PB Superflashes for years with no problems. Mine have never fallen off when hitting bumps, etc., and they put out a lot of light for an AAA system. I also have a Dinotte 140, which is extremely bright but expensive and difficult to mount. I would buy the Geoman/Magicshine over the Dinotte at this point.