We decided to try our hand at saltwater marine biology aquaria. Lots of stuff to learn about, and to read. Since we are not going to be putting in many fish, we won't be putting a high load on the system, so that means no sump. We still wanted a pleasing appearance though, so we left a little bit of aragonite on the bottom. The reason is that in a reef tank, the substrate cannot be gotten to under the live rock, and so it will build up anoxic pockets long term, and thus may pollute your tank.
Lighting is THE most expensive thing in a small setup.
You must have good lighting or your reef will suffer. Some people swear by them, and in fact this is what the power compacts use, though a special kind to make them smaller. They seem to be top runners. The actinic bulbs give the proper blue spectrum for special reef micro-organisms, and the daylight is for other organisms. Many people get 5500 or 6700K MH and supplement with blue actinic VHO lights, since High temperature MH lights can be expensive.