When I build computers for myself or someone else I tend to use mid size or full size cases. I like the expandability they offer for installing multiple drives, video cards and fans for cooling. I recently updated my Vail WHS 2011 computer to 18 TB of drives with 9 internal drives and one external for system backup. I filled the initial 5 tool-less drive bays and needed more space. I purchased two SYBA quad SATA II PCI cards and a nice Coolermaster internal drive bay. I would highly recommend it as it fits 4 HDD into the space of 3 DVD drive slots. It provides a drive cooler fan (LED blue lights) and is shock mounted. The box only cost $23.58 and is far superior to any single drive bay you can buy. It offers higher density of mounting, cooling, shock mounting and nice looks for your server tower. Here is where you can find it on sale:
http://www.newegg.com/Product/Product.a ... 6817993002I have added some photos for your info: