I'm using this machine for training and evaluating neural networks. It's also plugged into the internet, and serves as my server for quickly downloading and batch processing data remotely.
My main goals were to the GPU power and memory high, the cost down, and keep it quiet.
The X99-E WS/USB 3.1 has enough space for four cards. The manual that ships with it has some out-of-date information that made me worried, like it said that you could only run two PCIe cards at x16 if they were in slots 1 and 3. Fortunately this isn't true. I was also concerned that I would have to update the BIOS on the motherboard before I could use the CPU, but the board I was shipped (ordered from Amazon) already had the latest firmware.
This setup has enough space for 4 GPUs in theory, but in practice the MSI Gaming X takes up around 2.5 slots, so I would have to switch to completely different GPUs. The motherboard would also be operating at x8 for each PCIe slot with 4 GPUs, which can be a problem for some applications.
The 400Q case combined with the H80i help keep everything quiet. I work at the intersection of two busy streets, and I can't hear the fans over the noise of the streets.
I configured the fans for cool air to enter from the front and leave through the back. I used an extra fan from the H80i on the front of the case, and positioned the front fan that shipped with the case closer to the two GPUs. I found that the watercooling tubes from the H80i wanted to push on the top GPU, but with by zip tying them together it's possible to hold them back.
I had a little trouble figuring out the best way to run some of the cables, but eventually settled on running everything except the GPU power around the back of the motherboard. The ATX 12V power cables at the top of the motherboard had to stretch a little bit, but everything else was comfortable once it was organized. It might have made more sense to run the GPU power behind the back, because right now it's very close to stopping the fans on the bottom GPU. But if I did that, I would have to run the main ATX power differently, because they would overlap making it hard to put the sides on.
The additional hard drive in the photo is something else I had laying around I threw in.
Installing Ubuntu 16.04.3 I had some minor hiccups. Adding "nomodeset" to the GRUB startup helped me get a GUI for installing and using Ubuntu until I could install the NVIDIA drivers.