you could be right, maybe thats why the core 3 and 4 run 5 degrees cooler than core 1 and 2 at all times!
but yeah on the antec 300, which i have, the 140mm fan up is the larger exhaust. also at *idle* my cpu fan is running at 800rpm 120mm (Vendetta 2), with 30 29 25 26 right now, (been online for 6hrs).