I've got a set of Trident X @ 2400 MHz, 1.65 V and I've had no trouble with it just running passively cooled with stock heat spreaders.
These RAM coolers really aren't need much these days. It was more of an issue back in the original DDR days when the voltage was much higher. For instance, I had a kit of Mushkin Red line PC-500 that ran on 2.80 V IIRC. Now, that stuff was actually quite warm to the touch!