I'd used Panworld/Blueline's in the past. Loved em. Cheap. Quiet. I haven't ruled out external's yet. I feel better schooled on them than with submersibles. Externals do take up just that much more space, however. Since I'm doing an under tank sump this time around, that square foot a pump and plumbing takes up, can be appreciable. My skimmer is in-sump and the tank's 4x3 footprint may provied me the room to go external. Decisions, decisions......