I've had an IFX-14 on a Q6600 for about a year now. With 3 quiet 120mm fans on the main tower and an 80mm on the HR-01 it's quieter than the stock Intel cooler and very, very effective. Without lapping the IFX, I held top spot for air cooled Q6600s on the HardOCP OC database for several months.

I'll add that the IFX needn't be that expensive either; I got mine on sale for just a few dollars more than a TRUE 120. Well worth it for such an impressive and relatively rare accessory.