First you need to tell us a little about what you want, fish only, reef? Size of tank your looking at and do you plan on a sump, wet/dry or just a tank with some hang on back filters.
Live rock is a must have in any tank a min of 1lb per gallon is a good start. Sand bed and no crushed coral is the new school of thought. Underground filters are Old school and are known to trap waste over time and cause problems.
Give us some ideas on what your looking to have and we can better answer your questions.