I would suggest that if you build on a foundation of mud, don't be surpised if the house sits off center. I understand budgetary concerns. I'm not saying buy a $300.00 case, but try to get form and function and rugged construction over fashion and fancy materials that not only are harder to work with, but are noisier and more subject to RF interferrence. Here's how I prioritize choosing a case...
1) Do I really need to get a full sized case? Well, in my opinion, it would be best due to the fact that even if everything "fits" into a mid-sized case you want, it fits kinda like 5 pounds of the fun stuff packed into the 1 pound bag. This makes case cooling problematic. So even though you may not "need" the space, it is awfully nice and your PC will run cooler in the end.
2) 120mm fans are worth 3 80 mm fans for cooling. I know this sounds insain, but both specs and my personal experience have born this out. I have a Thermaltake case with like, seven 80 mm fans and I doubt I get as much flow as I would with three 120 mm fans. Ideally, the full sized case should have three 120 mm fans up front, and one in the side blowing in. Then two 120 mm fans in the back and one up top blowing out. With the power supply fan running, you will get a balanced flow. For a midsized case, you want one with two 120 mm fans blowing in up front and 1 in the side blowing in and 1 in the rear and top blowing out. You'll notice as you search... or at least last time I looked, there was no such animal on the market.
3) Get a steel case. What, no aluminum! You got it! Aluminum is noisier, harder to cut and modify without cracking the entire case. It is not as strong the way most cases come and is far more subject to RF interferrence than steel cases while costing lots more.
3) Chose offwhite or black and I'd go for black. Get an odd, fashionable color and not only will that color be out of style in 6 months, but it will look funny when you start adding optical drives to the bays that don't match. You'll end up with the quaint look of a Jamacian Road House.