dude cases are cases. some are better then others but there are a lot of cases. I took an old 10 year old case spray painted it metallic silver and built my computer in that, and it runs nice and cool. my system temp is only 96 f on load, and cpu runs at 110 f on load, idles at 77 f. whats important in a case to me is how much expansion room and how efficient cooling is. i had 2 mounting points for 80 mm fans, which i used at first kept it cool. i replaced one with a 120 mm, though i had to make custom mounts for that. nothin a good drill couldnt do.
my system: echo star 600w psu. gigabyte s3 mobo, amd athlon 64 x2 6000+
2 GBs of patriot DDR2 800, WD 500 GB HD. only using the integrated nvidia 6150E vid card right now, but hope to upgrade to the new ATI 3870 soon.