In order for dual channel to take effect, both sticks have to be same speed, size and specs (latency). Having 2 of the same brand name ensures that. Note that dual channel only gives you a 10-15% increase in performance but putting in your 2 sticks will definitely improve your overall performance. The more RAM the better.
Note that whenever 2 sticks of RAM with different speeds are used, the fastest will revert back to the slowest of the 2 sticks. e.g. 3200 would run at 2700 in your case. Even if your MOBO supports dual channel, it will not be enabled with 2 sticks of different speed or size.