JONSBO V12 Black Micro ATX Mid Tower PC Case, Hyperboloid Glass Desktop Design, Separated Cabinet Structure,Walnut Wood,MATX Desktop Computer Chassis, GPU<260mm,ATX PSU,Front 120mm*2(Built-in) Black

You should really poost on r/sffpc for buiilds or r/MiniPCs aboout what to buy for miniPCs. For mATX, I did a build out of space parts and a Jonsbo V12 case. It is a little bit larger cube than the game cube, but pretty simple to build with, with a modular or semi-modular PSU. You may also want to consider an ASROCK DeskMini or DeskMeet case/motherboard/PSU combo. A link to the case https://www.amazon.com/dp/B0F7R8QH44?th=1 Here is what it looks like. I like the wallnut: