Sumps for FW
is good if you have fish that produce a lot of waste because it helps dilute (probably better to have gotten a bigger tank though). I've been thinking about getting a trickle system too, but its just way too expensive. If you get one of these, then it will be impossible to grow plants (other than simple java moss and ferns) because the water is just way too oxygenated from the trickle. There are other ways to use a sump very effectively with plants though, but you can't have the trickle system.
The filter socks/pads won't get clogged if you rinse it as needed. They will act as a really good mechanical filter if you take a 5sec inspection for waste everyday.
I like to keep things simple and canisters are good viable options for big tanks. Since you have a free Oceanic filter, then just use it if you don't already have a good filtration system.