Which PC Case Should I choose?

Personally I would go with the Cosmos s if money wasn't an issue with my build but for a low cost system i would go with the storm scout

Link to a Monster review
http://www.modders-inc.com/modules [...] y&reid=273

I'm a cheap bastard, so i'd go with the cheapest case that would still fit your needs. Spend the money on components that make a bigger improvement.

I really like the Antec 300 for $50. Of course if you like all those kiddy lights and bling on your case, get something else.

Yeah, why waste cash on the case when you could spend it on what is inside?
That is not to say you should get a $10 generic white box, just that you should keep the price reasonable while ensuring quality and function.

If it were up to me, I would chose between the following cases:

Antec 300: $55: Great budget case. Good quality and cooling, low price.
Antec Sonata III with Earthwatts 500w PSU: $100: Great budget case if you also need a high quality PSU.
Antec 900: $107.50: Similar to the Antec 1200 full tower but a mid tower.
Cooler Master HAF Mid Tower: $115: Great design in a quality case that is good for water cooling.
Cooler Master HAF Full Tower: $140: Like the Mid Tower but larger.
Antec 1200: $172.50: Good quality with tons of space, tons of fans and ports for watter cooling.

As to which case you should chose, it really is more of a personal choice.
When you come down to it, as long as they has enough cooling, all cases will hold your parts.
Some hold them better and some hold them cheaper but they will all function about the same.