While I agree that Wet-Dry filters produce more nitrate, I do think a sump is very worthwhile. It gives you a place to put your hardware like skimmers and heaters, and it increases your water volume, which is like a cushion in case of a problem. You can make your own sump system by using a smaller aquarium, like a 20 gallon or 30 gallon tank, an overflow (you'll have to buy that probably), and a return pump, which could be your fluval. Don't put any bioballs or other media in it, unless you want to make it a refugium with Live sand or a DSB for nitrate reduction. You could also go to a local acrylic fabricator and get them to make you a sump. I had one made that was about an 18" cube and it only cost about $40. The advantage for the acrylic is that you can drill it and have a better pump to run the system, like an Iwaki or something. Most of the big reef books advocate using sumps.
Good luck,
Sonny