Upgrading the case will be very difficult. It's a Micro BTX "form factor". That's in quotes because Dell did a lot of proprietary connectors on those and except for a swap with an Optiplex 760 there's not much interchangeaability even amomg Optiplexes.
If you have The MT size case an aftermarket ATX PSU will work just fine.
The GTX 570 will cause huge fitment problems. The MB hangs on the left side of the case. The GPU is in the last available expansion slot. It will hit the CPU cooler. Even an ITX card needs modding to fit. Some of them a lot. The only decent video card that will drop in those is the Zotac GTX1050 Mini series.
BTX CPU coolers are not interchangeable with ATX.
A budget build of an Opti 780 MT would be a Q9650,Q9550...