New RAM at more than 2000mhz?

it depends on the rest of your system specs too , often its a safe bet to set your memory to auto in bios ,as it will set itself based on other factors such as processor type etc . to give you an example ,many AMD phenom chips have a memory controller set to 1333 as its native speed ,and motherboards will often set your memory at that speed regardless of what memory speed you have fitted 1600-1866-2000 etc , regardless of this you can of course override these speeds and effectively overclock (in some cases to distruction) usually you will get a warning if you attemt non standard settings .
set it at 1600 by all means but keep an eye on your system , you may start encountering "hangs" when using the internet or graphic reliant programs ,then you can try to switch back to 1333 and see if it cures it , but dont expect a noticeable rise in overall performance either way ,unless you are obsessed by speed and dragging every last ounce of performance out of your PC ,play the safe game . some motherboards will indeed allow ou to choose very high settings ,but will reset to safe settings during reboot anyway .
i know a few PC users that spend all of thier time constantly searching for speed ,overclocking and changing hardware at an increased rate ,and hardly ever use thier PCs for anything constructive , just for bragging rights ,but at the end of the day weather we decide to tweek or not ,the end result must be a reliable PC .

 

I use in my own computer


G.Skill Trident X Series DDR3 2400 mhz (original frequency, not OC)
it work perfectly
and now I don't want to change for nothing else.

 

my laptop bus is 1066 and ram bus is 1600

it is normal wont slow the laptop as if it was vice versa
so dont worry

regards