Hehe how much money you got...
Ok.. forget everything you know about freshwater... marine is so much more advanced...
ideally you want to drill the tank and put in an overflow so your taking the crap off the top of the water, protein/fats etc
The more costly parts would be: Protein skimmer, auto top-up system, powerheads/wavemakers? for water movement, sump, Lighting ie: metal halide/T5 tubes? and lots of other small bits n pieces that all add up!
you can buy quality German stuff that wont fall over and perform superbly and quietly
Or you can go chinese which youll eventually throw in the bin and end up buying the german stuff anyway