Yes, the Asrock H97 only supports up to 1600 mhz ddr3. This doesn't mean you can't use higher rated ram, it just will not run at a higher speed than 1600 mhz. Since your motherboard has 4 slots of ram, you can buy 2 now and add 2 later if you wish. I would however just buy 16 gb now, it will guarantee matching sticks for dual channel, and prices are pretty low at the moment. When DDR3 stock gets depleted prices are likely to go up.