Sump/Filter setup for ADA60 tank

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Im starting my first tank as an ADA60 17 gallon that i got for $150 with its stand. What sort of filtration is the current recommendation for a sump setup? I was hoping to make something equivalent to a filter basket setup with easy maintenance, so floss, puragen, chemipure and skimmer. I hadn't originally really planned for a refugium but the extra space could be used for one. Whats the current thinking for a good small sump layout?

 

I had planned to plumb in an 10 gallon sump to hide all the filters heaters etc but the dimensions of the stand dont really allow for a 10g tank to fit under there. Turns out there is a hinge piece that narrows the enclosure down to 9" so i can either do a 9X21 or 10X18. Realistically that either means custom shape sump or 5 gallon sump. Is a 5Gallon to small? Account for overflow the working volume will probably have to be close to 4 gallons  and that might be a bit tight.  Another alternative is an Ehopps RS-75  would fit in there but im not sure its worth the price or is super effective also id probably get stuck buying proprietary filters.

 

EDIT: Im leading towards just using an external canister. It seems to fit and I can get 3 stages of media in it.