Greetings.
As to what you need, it depends on what you want to keep. Do you have any lighting for the tank?
If you just want to keep fish, you can get by with NO fluorescents and the filter. If you are going the way of fish with live rock(FOWLR), you'll need to remove the filter media from you eheim and just use it for circulation.
You will also need aragonite sand, enough to make a DSB of 4 inches. The skimmer depends on what kind of livestock you are going to have, if they are messy eaters, you will need one. The chiller will depend on the kind of lighting you are going to have. The heater will be a good idea to have two, just in case one fails. One heater set at 82F and the other at 80F. As the wattage I'm not too sure if two 200W will be enough for the tank. The UV filter is a device which contains a bulb inside which gives out Ultra Violet rays to the water and kills any bacteria, parasites, etc. which are free floating in the water. You don't need one as long as you have good quarantine habits.
If you are going to keep corals, you will need two 175W MH bulbs and a couple of fans to keep them cool. You will also need a sump to help cool the water and aerate it. You will also need, to start, a bag of Instant Ocean salt for 50gals., you will need a hydrometer or a refractometer to measure the tank's specific gravity which should be between 1.024 to 1.026(NSW).
Hmmm let's see, I think I'm forgetting something. Anyone else would like to share thoughts?