I think all 1.5v ddr3 ram will run at lower speeds by default. It takes a bios setting to get it running at 1600.
But really, latency and speed are largely irrelevant for sandy bridge.
The current Intel cpu's have an excellent integrated ram controller. It is able to keep the cpu fed with data from any speed ram.
The difference in real application performance or FPS between the fastest and slowest ram is on the order of 1-3%.
Synthetic benchmark differences will be impressive, but are largely irrelevant in the real world.
Fancy heat spreaders are mostly marketing too.
In fact tall heat spreaders are a negative because they can impact some cpu coolers.
Only if you are seeking record level overclocks should you consider faster ram or better latencies.
Read this Anandtech article on memory scaling:http://www.anandtech.com/show/4503/sandy-bridge-memory-scaling-choosing-the-best-ddr3/1
DDR3 1600 is the sweet spot considering the marginal cost delta over 1333.