I have a 55 that I have been slowly improving that I think you would like to hear about.
I started out sumpless with a hang on skimmer and have greatly improved my system, if I can borrow a digital camera from a friend I will try and take pictures of my setup to show you. I have a 29gal glass tank in the stand that is divided into three compartments. Think about if you were looking at my tank straight on the sump is sitting to the far right and takes up about 3/4 of my stand. The other 1/4 is where all the electrical stuff sits. The first compartment is where the overflow from my tank comes in, where I house my heater, and where my skimmer is sitting. I studied skimmers for about three months before buying an Aqua C EV-120 (from skimerwhisperer) ran by a quiet one 3000 pump with a ball valve to control flow, which is really rockin for a 55, an Aqua C Urchin or Urchin pro would be just fine (or the others that Don and Mark have mentioned). The compartments for my sump are divided by glass panels that I siliconed in myself. I got the glass from a local glass shop for free, I just asked for any 12" square scraps. The divider between the skimmer and the center section is a bubble trap (three pieces of glass, the first siliconed to the bottom, the middle siliconed about an inch above the bottom, and the third siliconed just like the first with about an inch in between each), this will keep micro bubbles out of your display tank. The center is where the return pump goes, I use a Mag 9.5 with a ball valve to control the return flow (slow flow is best). The compartment on the left is for my refugium which has a deep sand bed with chaeto algae. The refugium is fed with water piped from my 9.5 as is my UV sterilizer. Many people have gone without a uv unit but I figure it is a good thing to have. I chose my mag 9.5 not to provide flow to the main tank but to make it so I can run several things with one pump. As for substrate, don't worry about live sand, the live rock will populate the live sand with all the living things you need.
As for not using a 55 as a reef, it is just fine, there are people with nano reef tanks all over and no one tells them their tank is too small. I see a 55 as the transition size to a big tank. Once you are addicted and properly experienced the big tank will come.
This is just my experience, for what it is worth.
Tim
