No, you'd be surprised to know that RAM frequency does not matter much in gaming.
See this video link :
http://www.youtube.com/watch?v=dWgzA2C61z4
In this video Linus Sebastian (most reputed techie on youtube) benchmarks and explains how even 2400 MHz RAM cannot show a noticeable difference in gaming FPS.
You're all right with 1600MHz RAM. No,need to buy a expensive one