Even IF they are all 'Matching' but not from Sets - there's NO Guarantees.
I can Guarantee e.g. 3 sets of 2X_GB, etc or 6 stick not to use XMP.
I can Guarantee e.g. Unequal Sized Channels kill Tri Channel
I can Guarantee e.g. Mix-Matching even RAM IC's (same Frequency, CAS, Voltage) will generate errors/problems.
I can Guarantee e.g. Frequency >DDR-1333 and faster the problems go up exponentially in unmatched sets.
RE: "I have 6 matching sticks of 4gb DDR3 Dual Channel 1600 ram is a really bad idea, the cut-off, now, for reliability placing together '6 sticks' is DDR3-1333. IF you start looking at 'Hexa Kits' you will quickly notice lack of Frequency/CAS choices. This is no accident, it all reliability related.
Bottom-Line, don't.