As you may remember, I'm in the process of building a PC for SWMBO. So far I have the Intel 2.8E CPU (Prescott), Intel 865GBF-L motherboard, Sony 700A Dual Layer DVD burner, Antec 380TruePower supply, 1GB of Kingston RAM, Windows XP Pro (OEM version), and Windows Office 2003 (student version). I still have to get a hard drive (probably a Seagate SATA), and a case.
In looking for a case I found that Intel has thermal specifications for its processors that have been translated into a case guideline called Thermally Advantaged Chassis (there is a version 1.0 and 1.1). You can read what Intel has to say about it here and a little more here. The second link includes cases Intel has tested and says will keep the CPU temperature at or below the 38°C (~100°F) maximum of the specification.
While I am sure other cases can also keep the temp below 38°C, you may want to consider picking your case from one of the companies on the Intel approved list (and perhaps replace their power supply with one from Antec). Or not. It's up to you. YMMV.
The problem I'm having is finding someone locally who sells any of the tested cases. If I try to mail order one of these I end up having to pay almost as much for the shipping (and in one case more) than the case itself! Oh well, just another example of the price of paradise.
Have a Great Weekend, Everyone - Aloha!