I already have a server at home server. I used a MZ32 motherboard with a bunch of disks 3.5" in it as it's mostly a storage server.

My HTPC is an old ATX desktop computer on its side in a Phanteks P400A case. On it's side it just looks like a black speaker grill front to back cooling it has three Noctua NF-A12x25 fans that are barely even visible.

The good thing about using standard parts is if the GPU died I could buy another cheap one to replace it.

But I guess that case is a cool idea if you didn't have those things.