The eSATA port is for a non usb type external sata drive or external drive cage. That's simply an extension of a sata port on the board itself by the addition of a long cable from the board to the front or top panel on many cases for use of a sata drive outside of the case itself.
The case itself will get mixed reviews for obvious reasons while seeing two 120mm case fans for air flow. A removable board plate for ease of installation is one feature other cases don't see. For the price however the case would generally be steel not aluminum. Need a variety to look over? http://www.xoxide.com/pccases.html
The power supply requirements and options will depend mainly on the type of build in mind there. If you are planning to oc, build a strictly gaming rig, or plan a work horse type with extra drives and devices then you look at the higher powered models. A great reference on how to choose the make, model, and power requirements is the sticky on supplies. http://www.computerforum.com/90118-useful-psu-case-guides.html
