When started this hobby jumped in with a 75g DAS AIO. Had a small compartment in the corner (~8x16") for the overflow, skimmer and pump return. Quiet as all pumps submerged and really no complaints other than pump return section sort small so would need topping up every few day or blowing bubbles.
Never really considered converting to put a sump under the display as couldn't see any great advantage other that increased size of display and volume of water plus hiding the heater. Did though think a basement sump directly below made more sense from the convenience factor.
Think AIO okay for small tank.
