Really, most any case with decent airflow will do the job.
By decent, I think two 120mm intake fans or equivalent will do the job.
Past that, it is largely a matter of personal preference.
If you love cases, spend what you need to to get a case that you live.
If you do not care too much about looks or "bling", then get a basic functional case.
One of the best positive pressure cases is the Antec 300 illusion for $70:
http://www.newegg.com/Product/Product.aspx?Item=N82E16811129066
A low cost negative pressure case is the Antec 200 for $45.
http://www.newegg.com/Product/Product.aspx?Item=N82E16811129074
Either will do the job.
If you will buy a GTX5.. or a GTX4.. or any other card, prefer to
get one with a direct exhaust double slot cooler that will get the hot air directly out the back of your case.