My last PC build, I actually went the other way. I got a fully modular PSU and went down to a Mini-ITX case and board. It's glorious. Tiny little box.
Assembly was actually much harder than I anticipated. I worked in data centers for years before I moved to my current position — I can literally assemble a PC (or server) in seconds once I get the parts on-hand. This probably took me about 30 minutes, because I had connectors and parts (especially that dang M2) on both sides of the board in the chassis, so I couldn't just install the board and build UP from it. Also, no quick-releases - they take up space that's at a premium. Screws are nice and small.