You'd be hard pressed to notice a real life performance difference DDR3-1066 and DDR3-1600. See:
http://www.tomshardware.com/reviews/memory-scaling-i7,2...
High End Memory Is Not Worth The Money
The results are obvious: going from one memory speed to the next, e.g. from DDR3-1066 to 1333, does not provide major benefits. Even the replacement of slow DDR3-800 RAM by DDR3-1600 memory will mostly yield disappointing results. While the performance advantage is measurable, it is never noticeable.
Where you do see significant differences is when overclocking:
i7-930 Stock
133 BCLK x 21 CPU Multiplier = 2.80 GHz
133 BCLK x 8 Memory Multiplier = 1066 MHz
i7-930 w/ 25% OC
167 BCLK x 21 CPU Multiplier = 3.50 GHz
167 BCLK x 8 Memory Multiplier = 1333 MHz
i7-930 w/ 50% OC
200 BCLK x 21 CPU Multiplier = 4.20 GHz
200 BCLK x 8 Memory Multiplier = 1600 MHz
So, as you can see...
getting 1333 memory allows for a 25% OC while maintaining the default 8 memory multiplier
getting 1600 memory allows for a 50% OC while maintaining the default 8 memory multiplier
You could get DDR3-2000 and up the mem multiplier to 10 at a BCLK of 200 but significant performance gains are not achieved and stability is often compromised.