In a decent case, no additional cooling is really necessary with current GFX cards, especially the non-reference designs like the Asus DCII series, MSI PE series, etc.
An micro ATX case on the other hand is by definition small and limited with regard to cooling. OK for a single card, non overclocked but I wouldn't advise OC'ing the GFX card or doinG SLI / CF in such a small case w/o doing something special.
Personally, I consider a mid tower with good cooling essential for single card systems and full towers for SLI ? CF systems.
Corsair 500R is a great start at only $90
http://www.newegg.com/Product/Product.aspx?Item=N82E16811139010