First off, that blowhole (fan centered over heatsink blowing air onto it) is a very good idea. For a good solution, Thermalright's SP-97 is an extremely good cooler. Coupled with a 92mm Vantec Tornado, you're sure to almost never have a cooling problem.
Also, have you checked the ambient temps and the voltages? Underclocking a CPU but leaving the core voltages high will still keep the temperatures up.
And you may want to check your AS5 job, and your overall mounting job with the cooler.
Athlon XP 2000+ @ 2.1 GHz
Corsair TwinX 1 GB Matched @ 2-5-2-2 clocks (took me a while to get that!)
Gigabyte VIA KT400 Ultra+ (SATA Model)
2x80 GB Western Caviar SATA @ RAID 0
Plextor DVD+/-RW 12x (712A)
Norcent 52x32x52x CD-RW
2x Pioneer DVD +/-RW 8x
8 USB 2.0, 4x Firewire 400