IMO:
aluminum cases - if money is of little importance, and you want that "coolness" factor. I would love to be able to get one of these. Very light, so great for lan parties as well.
chenbro genie or junior genie - A bit pricey, but great build quality and cooling ability. The genie is pretty big, but is one of the best in terms of cooling and modability.
Antec 1030 or 830 - Cheaper, good build quality, and good cooling. On the bigger end of mid-towers though. Great if you plan on having tons of stuff in your machine (this is what I have = D )
FongKai - Smaller and very quiet. If you don't need 8-10 bays the antecs and chenbro offer you, this is your case.
Enlight - Cheap and one of the most modded cases out there. Quality isn't as great as the other cases listed, but still a very durable case. (have one of these too

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