The biggest Sump you can fit under your tank, is the one I would go with. The more Water you have the better. So go with the biggest sump you can fit.
As for a top, some people use the Pond Nets, this allows for all the benefits of an open top tank, but it will keep your fish from jumping out. I am using a Egg Crate florescent lighting cover for my tank. Allows for an open top benefit, but hinders fish from jumping out.
Fish Sticks, the best thing you can do with your dead fish.