going to make my case like this
still considering 140mm fans
XIGMATEK 140mm fans : cheaper, sleeve bearing, dun like bling bling (if wan bling bling can add later, with bling bling hard to remove)
Noctua P14 FLX : Love it   but worried about static airflow and very expensive though
NZXT 140mm : don't know much about this... but some forumer here says good

120mm fans :
Arctic F12 : dun like white color but it already my best fan(lot cheaper than noctua one)
CM Stickeflow : i rather run delta 190cfm fan at 5v(119cfm at 26dba), i have a way to get it with cheaper price
XIGMATEK 120mm fan : bling bling again but sleeve bearing
or some china 120mm fan...?

CM90 CFM.. forget about it, damn noisy after half year

I always pay attention to the noise lol...
now can reach 4.8ghz at 71C without air conditional(afternoon hot weather)
night air conditional can reach about 66C max(avg), lowest can reach 57.5C(semi raining that night)

aiming below 60C at 4.8Ghz (i7 2600K)

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Added on July 23, 2011, 10:09 pm
why not?? put a hsf in front of airconditional u will know the difference

Normal Fans are bottom as intake and top as exaust
because hot air are thiner
they will goes up and cold air will goes down
u knows if u got study chemistry...