How to Build a Computer, Lesson 1: Hardware Basics
Just one thought on considering cases: The case will outlive every other piece of hardware in your DIY system. It makes sense to buy a nice one because it, unlike the video card or motherboard it houses, could easily last 10 years. That being said, a cheap case will probably last almost as long as an expensive one. Its all about the creature comforts you get to experience along the way. Flagged I absolutely agree. I agree, and personally I would avoid the cheap PSU's that ship with some cheap cases. I will also say that a good case is the foundation for a quiet, and adequately cooled, system that is easy to build and replace parts in. My home desktop is in a Sonata Solo which is not a terribly expensive case, but probably the best cast I've ever used in terms of how easily everything went in.
Related: E-Waste and the Future