[Solved] Will the AMD Phenom II 965BE support DDR3 1600 natively?

stay at the 1333MHz and don't ever mis-match..

AMD uses something called an IMC (Integrated Memory Controller).
It helps the AMD chips perform very well in memory related tasks (because now the ram isn't controlled by the motherboard through the FSB)
but it also has a few quirks.
The IMC doesn't seem to like a lot of stress, and so in general, you wont get as much of an OC out of your ram if you have all of your ram slots populated.
So it should be easier to get more performance out of only two sticks of ram.

*Intels Nahelem architecture utilizes this same design, leaving the Core 2 series as the only mainstream processor to still use the FSB design.

Also, the same thing goes for mismatched ram, the IMC just doesn't like it.
So if you have ram that is not from the same kit, and are experiencing instability, try taking out the non-matching set, and see if that helps out.

Also, you might have heard about the “timings” of the ram, and how that is important.
I have seen a lot of people get confused with that.
Let me explain this as simply as I can.

There is memory speed, and then there are memory timings.

Speed is the frequency that the memory operates at (in MHz... and remember that when you are looking in CPU-z that ram is DDR [Double Data Rate], so the frequency that it says will always be half of what it is actually running at). It is fairly straightforward and easy to understand.
And remember that the ram speed is tied to the reference clock, and in this way you can easily OC your ram beyond the stock speed.
Speed is mostly important for higher bandwidth, as it just means that the ram can move more information.

Timings are different, and should not be confused with the speed. Timings do not effect the speed (in MHz) of the ram at all.
Instead, they change how “efficient” the ram is. In other words, the timings affect the “turnaround” of the information.
The timings are generally listed something like this: 5-5-5-18. While I wont go into all of the details about what those each mean here,
I can give you a basic idea of what the timings mean. Timings change how long the ram will wait to do something.
So having ram with looser (numerically higher) timings, means that the ram will “wait” longer in between processes.
Using the example of 5-5-5-18 ram, information is copied, it then waits for 5 clock cycles before it moves onto the next step.
Ram with 7-7-7-23 timings running at the same speed (in MHz) will move the information there just as quickly,
but then will need to wait for 7 cycles between doing things, rather than 5.
This is why “performance” ram is in fact faster.