Dude here is a really good mid tower case that is compatible with mATX boards:
COOLER MASTER Storm Scout SGC-2000-KKN1-GP
It seems to have great airflow, and will fit pretty much any ATX power supply. Actually I would even recommend an
Antec TP-750 power supply for your specs. I have the 650 Watt version of this and I love it! Whatever psu you choose, be sure it is 80+ certified to ensure quality(bronze, silver, and gold are even better!). There are alot of cheapies out there that can wind up costing you more in the long run if things start breaking down because of a malfunctioning psu.