3200 MT/s Support Means You Can Use Any DRAM
To run pricey 3200 MT/s memory, you also need a CPU that can handle such a high data rate. Otherwise, your DRAM may only run at 1333, 1600 or 1866 MT/s, at best.
In the days of Intel’s LGA 775, CPU and DRAM overclocking was controlled primarily by the FSB (front-side bus). Let’s say you had a Q6600, and your motherboard supported a 1066MHz FSB. Left there, your CPU would run at its native 2.4GHz and your DRAM at 1066 MT/s. If you were to overclock the CPU by raising the FSB to 1333, your CPU would run at 3GHz and you could run DRAM at 1333 MT/s. In other words, the memory was limited to the FSB's ceiling. The memory controller (MC) was in the chipset—most often, the motherboard's northbridge—and ran at FSB frequency.
Now, the MC is in the CPU. So, if you want to run at your memory's advertised specs, the CPU is the primary factor. Haswell-based CPUs are rated at 1600 MT/s DRAM, and mid- to upper-tier non-K CPUs can typically run 1866 up to 2133 MT/s fairly reliably. For higher data rate DRAM, a “K” model CPU can be overclocked, thus helping the MC support more enthusiast-oriented modules.
AMD’s current FX CPU line is rated at “up to 1866 MT/s at one DIMM per channel.” However, you may find yourself running into problems with lower-end CPUs—and, at times, even the higher-end CPUs—running 1866 MT/s. This is partly because the MC in the FX CPUs is optimized for DDR3-1333 (according to the BIOS and Kernel Programming Guide). As with any CPU, FX CPUs can be overclocked to run even higher than DDR3-1866, but mileage will vary.