Get the live rock that loganj advises and skip the cannister. Cannister filters are nothing but a big pain in the butt if you ask me.
My preference for filtration is to run filter floss at all times, and my water is crystal clear with a high bio load and never using any other filter medium. I built my own back filter to do nothing but house gobs of filter floss, and it works great.
Water flow is your biggest concern. For a 55gallon I prefer a couple of high volume back filters such as Emperor 280/400 spaced out evenly, or a single big back filter in the middle with two 200gph power heads in the corners. I'm steadily moving away from horizontal firing powerheads and using back filters again simply because back filters are more efficient at moving water from the top of the tank to the bottom. Much better for oxygen exchange and less disruptive for fish.
Get enough live sand to cover the bottom of the tank 2" or so. The 'biological filter' capabilities of live sand are hype, but it's far less messy than dry sand, and worth the money in that respect. My own experience is that sand beds beyond 3" don't accomplish much other than displace water.