I know this is probably not the right solution for you, but I was going to purcahse a 550EX or a Sigma 500 DG Super. I ended up buying an Alien Bee AB800 with stand, umbrella, strobe, and carrying bag for $349.00. I loved it so much I ended up buying two.When I compare how much money I was going to spend on on-camera flashes I think I got a deal. I will never go bacxk to on camera flash.
I have a Vagabon Battery system on order and will be able to easily shoot group shots indoors or out...