The processor's integrated memory controller does its best overclocking work when 2 memory sticks only are used. This includes any using DDR3_A1 and B1, or, DDR3_A2 and B2. When you use 4 memory sticks, the processor will set default 1333MHz 9-9-9-27 timings in the BIOS. Getting to 1600MHz will require a minimum of 1.65 volts and the frequency selected manually. You are in fact overclocking which may or may not work depending on your motherboard and processor.
I'd suggest starting with slots DDR3_A1 and B1 setting the memory timings to 1333MHz 9-9-9-27 and 1.65 DDR3 Voltage manually. Save the BIOS settings and confirm the system is stable. If it's stable, power down and insert the second memory kit. If the motherboard and CPU are running optimally, the system should now accept it.
I have had the Extreme 4 and Extreme 7 which have worked well with many different memory kits. Hopefully your board is up to the task. Consider flashing the BIOS with ASRock's software if your board isn't up to date.
I am not a Patriot Memory employee. But, I am very happy to help and understand that everyone needs a little help now and then figuring some tech. Keep in mind that Google search can help you find other computer hardware related forums where you can often offer similar or related answers.