The latest fans from Vantec are of the speed control variety. We tested them as standard case fans, and as a possible fan replacement for our heatsink fan.
"We also tested the Thermoflow on an Athlon 1700+/Swiftech heatsink. Previously, the combination was equipped with a Thermaltake Smart Fan 2. Load temperatures after 20 minutes of Prime95 were 49C. With the Thermoflow, temperatures were unchanged, although the Thermoflow ran much quieter."
News source: Viperlair