Upgrading My RAM

[Demoz775]

Hello there. Im thinking of adding some RAM to my dekstop but im not sure if its worth it.
Im running single 8GB 2133mhz corsair vengeance pro RAM atm. I wanted to upgrade it to 16gb but the corsair company provides 4x2 gb and 8x2 gb only, im not sure what should i buy. Shall i take the 4x2 2133hz or the 8x2 2133mhz (if i would go for the 8x2 its going to be 24GB altogether then)
My other pc specs:
-GTX660 2gb
-FX 8320 3,5 ghz

 

[Tradesman1]

If upgrading go the 2x8GB - that way you aare guaranteed to havbe 16GB anyway - there is no guarantees that the new DRAM (whatever it is) will even play nice with the old DRAM