wow

I am planning to have a 3 ft tank for my marine aquarium, and I was wondering which filter system would be the best, for a tank that size. The tank will be 90 cm x 45 cm x 50 cm. I have an EHEIM 2217 that I can use for this tank, but I was wondering if an external overflow, with a sump system underneath, would work better? My plan is to fill the tank with rocks (mostly dead, some live and coral), and fishes. My concern is to keep the tank's outer apparance to be as 'clean' as possible, as it will be situated in my living room. What are the drawbacks of using the EHEM 2217? What are the advantages? Likewise, what are the drawbacks and advantages of using the external/sump system? For those having 3 ft tanks, what have worked out best, in terms of easiest maintenance (I know it sounds naive, but we can hope right ?) and cleanest look? Any alternative besides the two systems above? Last but not least, what sort of rock/coral/fish that you'd recommend to fill a 3ft. tank with? Thanks in advance for everyone's time.