I am attempting to breath some life back into an old machine – i5 2400, Gigabyte Z68M-D2H, AMD Radeon HD 6950, 12GB DDR3, 120GB SSD, Windows 7 64bit. I have a DUAL channel motherboard with 4 slots (white and blue coloured slots). Support for DDR3 2133/1866/1600/1333/1066 MHz memory modules The following sticks available: 2GB DDR3 @ 1600mhz 2GB DDR3 @ 1600mhz 4GB DDR3 @ 1333mhz (heatsink) 4GB DDR3 @ 1333mhz (heatsink) I am seeingk advice on what is the best configuration for performance. Will the memory run in DUAL channel if its mixed sticks? Should I just attempt to push all sticks the 1600mhz, considering the slower sticks have the heatsinks? Is this dangerous for the memory/motherboard?