Does DDR3 memory Speed really matter in gaming?

Solution
You want your RAM to be 1600Mhz min. 1.5v preferably (the 1.6v ones are older tech, for that speed at least). Cl 9-9-9-24 is a good base. Lower CAS is better.
with an APU (built in graphics cards into the CPU) the ram speed is very important. with chips without a GPU built in, like the AMD FX series 1600Mhz is usually good enough, anything over 1866Mhz prob wont be felt in games performance