your not going to really notice a difference. bench marks show that theres 1-2% difference in gaming. 2000 oc means you can run ram up to 2000mhz. anything below that as well. having more mhz in the ram is better for over clocking your cpu. it gives you more head room. 4 gigs at 1600mhz is realisticly all you need. anything more wont make a difference unless your doing lots of video editing or rendering things. but like i said if you want to over clock ur cpu lots its better to have head room in the ram.