Because they don't look to achieve visual perfection, these workhorses tend to offer a lot of room for expansion; and that's even the case for micro-servers. Models from Lenovo, HP or Dell will often offer several PCI Express slots and vast amounts of space inside to ensure adequate air flow for cooling.
A mini tower will routinely hold four RAM slots with enough space for four standard hard disk drives, for a total of around 40TB. And because they are actually designed for easy maintenance, you will find small details like a tool-less case and a built-in tray to be surprisingly useful.
