If you already have canisters laying around you're not using, then throw em on there. I wouldn't buy new canisters if you already have a sump, though. Adding a couple filter socks is way cheaper. The problem with adding more foam/pads is that stuff is getting around them into the sump--and there's more to clean/change. I think it's a lot easier to change out a couple filter socks than replace/clean a bunch of foam/pads in a sump. But, if you don't have space, that alters your decisions, too. No space to easily swap socks, they're not much fun to use, either. Pads might be better in that case.
I guess you could live with it in the sump, but I'd think it's not good to have it on your bio-media.