Getting into the Xigmatek Nebula couldn't be simpler: three of the panels are removable without the need for tools. The left, right and front panels simply pop out of place providing access to the internals. The base, top and back are fixed in place and cannot be removed.
Inside there are two 3.5" bays with tool-free retainers. One of these bays can be used to house a 2.5" drive with an adapter. Additionally, there is also a single dedicated 2.5" mount.
Along with room for a Mini-ITX motherboard there are also two expansion slots for dual slot graphics cards. While Xigmatek claims the case can support 200mm-long cards, there is a catch.
We found that only single slot cards were able to measure 200mm long while dual slot cards couldn't be longer than 175mm. This is because that orange activity light in the bottom right corner of the faceplate is recessed 70mm back into the case blocking longer cards. Xigmatek seems to have favored form over function.
If that's a problem, however, we discovered that the orange light and its cover are only secured by two screws. If removed, the case can handle cards up to 245mm long. What's more, without this piece, the case looks and works just as well as it did previously.
Aesthetics take priority when it comes to GPU ventilation as well. The GPU fan is blocked by a non-ventilated side door that significantly limits airflow. A solution would be to put an extra slot's width between the GPU card and the case door to help improve airflow, but this seems like a waste of space.
Speaking of wasted space, because of the Nebula's internal layout, you can expect to have a huge 260mm x 80mm x 120mm cavity that is completely unoccupied regardless of what hardware you install. Roughly 13% of the internal space isn't used. At best, you could run some water-cooling hoses through here but they still don't require that much space.
Despite all that unused space, the Nebula is still limited to a maximum CPU cooler height of just 80mm. For the most, part low-profile heatsinks have to be used. That's not a huge problem as most Mini-ITX cases face the same problem, but being such a tall case at 330mm we had hoped Xigmatek came up with a way to fit full size 160mm heatsinks.
The CPU cooler's headroom is limited because the power supply is oriented vertically rather than horizontally. Vertically, the PSU measures 150mm but horizontally it would have been just 85mm tall -- 65mm more headroom. A total of 145mm would have allowed for a much broader range of better performing heatsinks to be installed.
The Nebula is cooled by a single 120mm exhaust: a silent Xigmatek XOF fan that spins at 1200RPM. This fan is designed to remove hot air from the case while drawing cool, fresh air in from the bottom vents.
The Nebula's internal design is a little underwhelming. Given the space available we feel Xigmatek could have been far more innovative. Perhaps that stance will change once we actually install hardware.