I agree with OP about canister filters - they're inherently "dangerous" things (from a leakage point of view). A well-done overflow is much safer. A hang-on-back is almost infallibly safe.
Sumps are best - you can add huge amounts of volume (I have 40 gallons on a 150 gallon tank) and have absolutely massive amounts of hidden space for equipment, grow-out refugium areas, etc.
OP: if you can't do an overflow and sump I would probably hang 2 AC110s and use koralia-style powerheads for any additional flow you want. The emperor 400 is a really annoying filter, although mine has lasted me quite a long time. The vertical filter media sucks, the default filter cartridges suck and it's hard to add loose media. The 2-piece impeller on mine gets into a weird state and makes a bunch of noise until the filter is unplugged a few times to torque it back into position.
