Regardless of what the RAM is rated for AMD only officially says that your RAM max frequency is 1333MHz.
I hope I'm not reading your mind wrongly here... but, yeah, this is wrong. AMD rates the memory controllers at 1333Mhz for the purpose of the lack of need for anything faster due to current memory standards that OEM manufacturers use in their prebuilts. AMD memory controllers can actually run at 1600Mhz due to an undocumented x8 multiplier, without bus clock OC-ing. The same goes for Sandy Bridge: rated 1333, multipliers allow for much more. Memory speed capability is mostly IMC revision specific. His, being an E0, should run 4 DIMMs of RAM at 1600Mhz no problem.
Fourth, you can't simply just set your RAM to 1600 and expect it to work.
If it's rated 1600Mhz, it's going to work, unless the RAM is DOA, or you run on an IMC that's actually known for problems running high speeds (i.e. C2 revision, but they don't make the Phenom II x6 in C2 flavour)