Yeah, it's rough paying boutique prices for a top notch case from a small batch supplier. But you get what you pay for, and I am personally extremely impressed with the build quality of my $350ish (with extra panels, PSU plates, accessories, etc.) Cerberus X. Now if HDPLEX could hurry up and deliver their damned 800W DC-DC PSU, I could finish the damned thing!
But to be clear, as much as I am quick to defend the economics of small case builders like Dancase, NFC, and Chimera, I get that it's boutique for a reason. Most people don't need/desire that level of quality and customization. Nevermind the people that simply can't afford to throw $300 at a freaking case.
I've gotten some pretty garbage $100ish cases though, so try not to be too quick to just buy the cheapest thing that'll fit your motherboard. Also make sure it has the room to fit your desired HSF, cooler, full length GPU (including height!), HDDs, etc.
This is getting long but...
Quick question, why do you want/need a full ATX motherboard with those minimal requirements? Why are you wasting your time with a GT 620? I'm pretty sure the onboard Intel GPU would run about as well, and the $80ish you'd be spending on a GT 620 would be better spent on an RX 550, or stepping up to a GTX 1050.