Not to be overly silly but you can also save some money if you do something more unique than a case. A few years ago, I had a PC I assembled on a piece of plywood and hung as wall art.
I'm tempted to do that again since it had a footprint of "zero"
... though with a "hotter" unit I'd probably do something underneath hotzones like the cpu itself. Probably just using mobo raisers is enough though.
Just be sure to design it so that all of the cables aren't stressed by gravity. If you do want a box its kind of interesting what will work as well as a case for free..... just google for case mods and get some ideas.