24cfm is starting to get weak but should be fine for sub 3.0ghz cpus....I had a 45 cfm 80mm ystech fan on my alpha 8942 which I needed to hold my 1.6a@2.74ghz (1.71v) within sub 60c range....
I go with more of a balance.... I have 2 intakes (1 lower front and 1 side fan) and 1 outtake at back of rig and count my PSU as one outtake. It draws air from top of the case and not from the underside of the PSU like many.
With my P4 system I ran 3 intakes and outtakes....barely kept the temps from 70c...range was 58-66 (depending on time of the year)...system temps were 25-32 (idle to load)...aux temp hit 41c sometimes....
NOw with less I run 49-51c load cpu....system is 21-24c (idle to load)....
All that damn cpu heat was stil heating up my computer. I have a more powerful vid crad now that generates more heat and yet my case temps are way down...