Word of advice. Depending on your budget, go for a full-tower. It also depends on which graphics card you will use but most of the newer generation have gotten longer and now there's all these fancy coolers on them now.
I don't know how many drives you will have but it's always better to have spare room than trying to rearrange hardware and try to make room.
If budget is an issue, then yeah, your options become more restricted and you're probably looking at mid-tower cases.
I bought an Antec Solo and although it's a great case, I didn't give myself much room for such developments of video card sizes. I don't know why they have to make them so huge as you think technology advancing would result in a smaller frame. Go figure.
Anyway, I suggest a full-tower if you're a gamer. I know the choices aren't as good and the prices get higher but you might be thanking yourself in the long run.
Question remains, though, which one?