Originally posted by: Ero-Fan
your method of cooling makes more of a difference then the case itself.
This is true, but not the whole truth. The case design affects greatly how well the active cooling (fans) works. A crappy design wouldn't allow the air to flow intelligently through the case, and the excess heat wouldn't be removed efficiently.

However, this has little to do with the material of the case. Maybe an aluminium case with its superior heat conductivity would enhance passive heat dissipation a few percents, but that hardly matters in the end.

Masamuneehs gave the best piece of advice...