This question is a loaded topic. So many factors are at play, the most important of which is what livestock you intend to keep and how big the tank is.
Wet dry filters have been used for years to create successful marine systems. They are very efficient at processing ammonia into nitrite, and nitrite into nitrate. The issue is that most marine livestock struggles to maintain maximum health in systems with rising nitrates. Water changes can help to limit nitrate, but the constant tinkering with the environment is stressful to the livestock.
If at all possible, I would look at options that include natural methods of filtration. For example, you can order dry rock at a huge discount. I filled my 180 FOWLR with dry rock from Marco Rocks The finest aquarium rock available, base rock, live rock, reef rock, marco rock, reef tank saltwater fish, live corals, Marco rocks, Fiji live rock, Tonga Live rock
. Within a few short months it becomes live.
At minimum, i would like to see you utilize a deep sand bed of 4'' to 6'' aragonite sand, and a protein skimmer. You could design the sump so that all water flows first into the protein skimmer, with the output of the skimmer directed over the wet dry filter. This would allow the skimmer the opportunity to remove organic waste, so that less organics flow over the wet dry bed producing Nitrates. Take a look at the CPR brand sump systems for an example of how this works. It is pretty simple to design if you are handy, just by using counter current air driven skimmers as part of the sump.
Also, do not underestimate the ability of live rock to process waste. It does not take near the amount of rock that you might expect, especially when incorporated with a deep sand bed. You could certainly begin with the use of a wet dry filter and skimmer, and then slowly add live rock, removing sections of the wet dry as you go along.