Carl,
Many binding posts require 1/2" holes on 3/4" centers. RCA jacks vary, some are 7/16" but you should measure the ones you are planning on using.
I cut IEC openings by carefully laying it out, drilling a 1/4" hole in each corner and using a coping saw to cut the sides. Finish it off with a smooth file. Since the lip of the jack will cover the edges they don't have to be perfect. I have done several chassis using this method and the IEC's look like they were born there.
I cover the chassis with 2" masking tape before working on it. It makes laying out the hole locations easy and prevents scratches.
I suggest buying a set of high-speed bits covering from 1/64 to 1/2" by 64's (assuming you don't have some already). This will give you just about everything you need. I also suggest the use of a step drill. A common one is the "Unibit". These work great for sheet metal such as a chassis. Regular bits can tear thin metal.

The Delta tools are pretty good if you don't buy the bottom of the line. The $99 special at Lowes or other home centers is what I would call "fair". I have owned one and was disappointed as the chuck was really bad and some drills would run straight and others would wobble.
mike