My "main" system is an Epox 8K5A2 (KT333)/XP1700 "A" at 1879MHz in a Lian-Li PC-65, which has 4-80MM fans. The HS on this system is a Coolermaster HHC-001 with a Titan aluminum 80MM fan (38CFM/28dB). Temps for this system typically run about 25-28C system, 32C idle/40C load for the CPU. Most of the time the exhaust fans (top blowhole/rear) are running on 50%. The 2 front intakes usually run about 75% unless it's a warm day.
The 2nd system is an Epox 8RDA+ (Nforce)/XP1700 "B" at 2205MHz (11x200) in a funky Globalwin aluminum case I won in a contest. HS is an SLK-800a/Panaflo H1A. The cooling on this system is a little more extreme...there's 1-H1A and a Panaflo 120MM L1A (side panel mounted) as intakes, with another H1A as rear exhaust and a 120MM Panaflo L1A top blowhole exhaust. This system runs 20-24C for system temp, 34-37C idle/40C load temp for the CPU. Even with all these fans, this system is very quiet since the fans are usually at 50%.
Have the rheobus setups allows total control over the fan speed for intake/exhaust. They are very reasonable now, usually under $30, and are sold most everywhere. I used the Sunbeam brand, which are available cheaply at
SVC.