Why do you feel that is not enough? Do you use applications that require large amounts of memory or are you multitasking and notice a lot of hard drive activity and slow downs? If so more memory can be a big help indeed.
Memory speed is hardly worth worrying about so much. 1600mhz memory is plenty fast enough and faster memory really only results in very small differences you never see in actual daily use.
If you just feel that you want things to be "snappier", I can attest that nothing in the world will make your PC more snappy than loading your OS onto a good SSD! Bang! Talk about snappy!
It DEPENDS on your CPU and USE. LGA 1155 then Vengeance or Ripjaws X - best to use 1.50v RAM. Otherwise, other than a DDR3-1333, the Dominator's are 1.60v~1.65v and are IMO better for say LGA 1366.
Problem - The Vengeance are not as good, in comparison to other Sets nor the Dominator, for OC'ing (higher than Rated).
Problem - Gaming on the LGA 1155/SB, there is no benefit >DDR3-1600 with the SB. However, the LGA 1156/1366 'do' see an advantage to >DDR3-1600 IF the CAS Timings are ALSO LOW or 2~8FPS increase. Further, to use >DDR3-1600 you will need an AMD 4 core (~DDR3-1800+ limit), AMD 6 core (~DDR3-2000+ limit), SB (~DDR3-2400+ limit) and i7 9XX (~DDR3-2200+ limit).