Hello to New York!
Welcome to the 200 gallon club. I am not an expert, and if Im wrong, I am sure I will be corrected by others. Best advice so far that I saw for you was to read, read, read... Asking questions isnt a bad idea either.
IN MY OPINION... :
5800 gallons an hour is way much.. At 200 gallons, thats turning the tank volume over 28 times an hour... whoa... how long would it take to fill your 55 gal sump at 5800 gallons an hour. I dont know what overflows you are using, but you better check the volume rating on those bad boys, or you might be in for a wet surprize! :-O If you are looking for flow, I would recomend (no expert, remember) that you get most of the flow from powerheads, such as the tunzies, vorteks, or perhapos the korillas. I use the korillas myself. Its been a while, but it seems the rule of thumb is like 5 to 15 times the tanks volume per hour. Mabie 20 if you absoloutly have to have the bigger dog on the block. The reason to take water to a sump is to increase the total water volume, and to do your "stuff" to it out of the display tank. as long as the flow will feed your skimmer and all the other goodies under your tank, thats all you need IMHO... If you absoloutly have to push 6000 galons of water through your tank per hour, I would suggest doing most of that with above mentioned powerheads.. Especially if you are considering a FOWLR. You would hate to pay the money for a pump only to find that it drills holes through your fish...
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Think long term and buy good equipment, so you dont have to buy over again later if you deside to go in a different direction. Buying a tank is the cheapest part of a big tank setup. I have more money tied up in rock than I do the tank itself. My controller cost more than the tank itself, and my lights were more than the tank itself..lol You can go simple or elaborate.
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Start simple with an eye to expansion, Its insane what I have spent on my tank just to keep my rocks alive ;-) There are many good skimmers out there, just make sure to get one rated for over your tank AND sump size.
The auto top off is a good idia, but you will figgure that out yourself after lugging enough buckets around. A 200 gallon tank evaporates a LOT of water, and if you dont keep up with it regular. your fish will be walking on salt before you know it. I paid like 100 bucks for a level lock at bulk reef supply, and it was some of the best money I have spent in this hobby. ts hooked up to my RO system on a timer, an d it is only powered up for 15 minits, 3 times a day. Besides, it keeps the salinity steady, and that is only good for your fish. There are a lot of good setups for auto top off's, and many are less expensive than the one I have.
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UV sterilizer?.... mabie later, mabie not
Chiller?... with no corrals right now, and assumong you arnt running MH lights, probably not, at least from your description. I have ran my 200 for years without a chiller. Sometimes during the hot part of summer, I have to keep the AC turned on in the house, but I run 2x400 MH lights with some vho's (getting rid of those this week for a 72" constilqation.. yay!!)
I forgot what elce I was going to say, perhaps a flashback going on here..
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Enjoy you new big glass water holding box
Jeff