Suggestions?: 120mm PWM Fan for CPU

I'm looking at trying out a couple PWM fans on my heatsink. I currently have a pair of Scythe S-FLEX (1900rpm) fans in a push-pull configuration on my Venomous X.

What I'd like to do is replace them with a pair of fans that provide the same or better cooling under load but run quieter when the machine is idle. What do you guys suggest?

This Scythe is available at the local shop:
http://www.memoryexpress.com/Products/PID-MX30342(ME).aspx

Thoughts?

Cooler Master Blademaster - it might be quite loud at high speed but is a very nice fan and isn't obscenely priced like the obscene Akasa Apache/Venom. Obscene.