DX58SO Memory Configuration

Hello,

I own DX58SO, with Intel Core i7 920@2.67Ghz, with 3x2GB DD3 PC3-10700(667MHz).

I want to update to maximum RAM configuration and i wanted to ask exactly what kind of kit should i buy. I have heard something about 4x4GB @ 1600 or even 4x8GB.

So, what would it be the most reliabe and fast configuration i should go with?

Thank you.