OCC has published a review on the Kingston HyperX KHX1600C9D3K2/4G Memory

The Kingston HyperX KHX1600C9D3K2/4G kit of memory impressed me with its performance and quality, but one issue I did run into was stability. I had to set the voltage to the maximum required setting of 1.9v at all times to run them at the listed stock timings of 9-9-9-27. I manually set the voltage at 1.7v when I first installed the memory and raised the voltage slowly until stability was achieved. However, before the 1.9v mark, my computer would crash during any program that stressed the system, such as gaming or benchmarking. I assume that some kits can run stable below 1.9v, but the set I received could not. With the voltage aside, the HyperX kit ended up on par with or ahead of both the Corsair and OCZ kits in most of the benchmarks and was also able to average a few more frames per second in Left 4 Dead across most resolutions.

Kingston HyperX KHX1600C9D3K2/4G Memory Review