I finished this personal project while working as a technical support engineer for Intel. My purpose was to design a very small and powerful audio PC. I modified 1U server case to host components. With only two fans (CPU and case), it stays cool under full load. Its PSU works around 25 dB when loaded. Case fan (Nanoxia) takes cold air into the section of audio interface and SSDs to cool them down. As a result, it works up to 46-50 Celsius at load. Its volume is around 4.8lt. You can find exact dimensions in this excel file.
Main components: Gigabyte mini-ITX board, i7 CPU, RME Hammerfall 9632, 3xSSD, 16GB Ram, Seasonic 250W PSU, 1U server case, Zalman and Nanoxia fans.