I'm shopping around for a radio slave kit. My intentions are to help me shoot better night pics of BMXers and skateboarders. As of now I'm still rocking my Canon Elan 7e and my 550ex. I 've looked into the SE2 transmitter for my 550 but I've heard the 550 must be in front of the transmitter to work. I'm interested in radio slaves so I can put my flash anywhere and have it go off when I tell it to. If anyone has any suggestions for a first kit that would be great, price concious if possible, but I know these things start to get expespensive. Any help would be great! thanks -Justin