this is my personal take on the wet/dry and even pre-made sumps, everyone has a right to their own thoughts and opinions. i feel for what they are they are to much money. these filters are excellent freshwater filters as the bio-balls provide plenty of surface area for biological bacteria to grow, not so much in a saltwater tank.
the very basics of saltwater filtration should be enough live rock and water flow, add a very good skimmer, carbon/phosban reactors, a refugium and you should have no problem reaching 0ppm nitrates.
if you can find a used tank off craigslist or if you have one laying around you can make a sump for the price of a few plexiglass sheets ( you can also use glass but its going to have to be cut exact, which glass shops usually will do for free but remember-exact. plexi cuts smooth on a reg. saw blade ) there are alot of youtube videos that show the construction of a sump or if you have questions, ask.
as for my refugium i currently have 2 small pieces of live rock for pods to hang out on, a clump of chaeto macroalgae ( which really provides plenty hang out space for the pods ) and a 6 inch sand bed. i also have a few pieces of kenya tree and xenia that when i see in the display i throw down there to prevent them from over-running my tank as they both grow fast. ive been waiting on a guy to give me other macro algaes for my refugium but havnt had a chance to meet up with him yet. my plan is to grow them for a food source as well as something to look at in the display if theres a good supply growing in the sump. all you need is the chaeto but ive been looking for some new macros for awhile now. i personally avoid any of the caulerpas. my refugium light is just a 6500k full spectrum work light that currently is on for 24 hours a day ( i just rotate the clump of algae every other day or so ) but usually is on a timer to come on alittle before my tank lights go out and turn off alittle after they come on.