My solution was to add a $25 LSI SAS9201-16e HBA card to the server, and DIY build a DAS Tower enclosure to connect it to. 16 extra drives for the server, for under $300. No hot swap bays, but still 100% toolless drive swapping thanks to the drive cages used. My $300 DIY 16-drive DAS Tower build goes into full detail of my build. Could expand to a 24 drive tower, if desired.