Sizing up a case is pretty easy, just make sure it will fix an ATX board, and you're fine (with the exception of some giant CPU fans). And yea, HTPC cases are probably too small for a monster system. You want room for an ATX board, a big video card, and a giant CPU fan. But pretty much, all you have to do is make sure stuff will fit in it, and then pick the features, price, and brand you want. All there is too it really. From personal case experience, I'd suggest Raidmax, Cooler Master, NZXT, or Antec. Do NOT, repeat, NOT, get an Apevia case. I did once and I hated that bloody thing. Awful.
My personal case is a Raidmax Blackstorm. MmmMmm, good stuff. It was made for system builders, and it shows. The motherboard tray is on a fold out door, has a mesh side panel, a HUGE sidefan, very high quality build (no cuts!), fully tool-less, on and on and on. My only complaint is that its harddrive removing system doesn't work if you have a large video card installed. But that's easily solved by the motherboard tray .
My personal case is a Raidmax Blackstorm. MmmMmm, good stuff. It was made for system builders, and it shows. The motherboard tray is on a fold out door, has a mesh side panel, a HUGE sidefan, very high quality build (no cuts!), fully tool-less, on and on and on. My only complaint is that its harddrive removing system doesn't work if you have a large video card installed. But that's easily solved by the motherboard tray .
AMD Threadripper Pro 5975WX PBO+200 | Asrock WRX80 Creator | NVIDIA GeForce RTX 4090 FE | 64GB DDR4-3600 Octo-Channel | Windows 11 23H1 | (details)
MacBook Pro 14in | M1 Max (32 GPU Cores) | 64GB LPDDR5 6400 | macOS 12