I don’t have a good answer for a small prebuilt that does take 2x 3.5" drives, but I can confirm that there’s not enough physical room in the S01 for 2x 3.5" drives. A single 3.5" drive plus a single 2.5" drive, and potentially a second 2.5" drive if you swap out the optical drive and get a slimline SATA adapter, are all you can fit. That’s all the power and data connectors that are available as well.