last pic showsthe top off the tank in hot wether. I will soon have a heat plate exchanger to keep the temperature down.
now to answer your question, keeping marines is not harder if you get the right equipment. it is alittle more time consuming (ie more equipment to clean). of coarse, you don't need a big filter system, a lot of people use a couple of external filters live rock and a few powerheads in the tank for water movement which is relativly inexpensive.
the reason that my filter is so overated is because it I keep some of the more demanding corals such as SPS (short polyped stoney corals).
if your willing to put time , effort and money into it, then I say givi it ago but start with easyer species or even a fish only tank.