A case may seem A fairly unspectacular computer component but it if you get your choice right you may not need to change it for years, you can just upgrade the motherboard, processor and memory for a fast more up to date machine. If your going to keep your case for a while you can afford to spend a little more on it which is exactly what I did and am now very happy that I did.
The case I have now is a lot better build than anything a pre-built PC came in! It all depends on what you want but I wanted something that was solidly built and stylish, mine has a hinged front door panel that’s lockable but keeps all your CD and DVD drives tidily behind and protected from dust, speaking of dust the air intakes for the case also have removable and cleanable dust filters, The side panel is also hinged and opens once a couple of thumbscrews have been taken out, it also has cushioned drive bay to help protect your drive and also it minimises acoustic noise from them, the whole case cuts down on the noise produced by the computer and comes with plenty of front mounting options for sound and USB. All in all I wouldn’t want to change back!
The model I use is the Antec Sonata III 500, I’ve built 3 systems using this case.