laptop - Which RAM will suit my notebook ACER Aspire 5820tg 1333MHz or 1066MHz what CAS

I have my ACER Aspire 5820TG - 433G32Mn and want to upgrade RAM memory.

Currently it has the following components:

CPU: Intel Core i5 430M

Mainboard: Acer ZR7B

RAM (3GB): 2048MB DDR3 PC3-10700 (667MHz) Samsung M471B5673FH0-CH9
1024MB DDR3 PC3-10700 (667MHz) Elpida EBJ10UE8BDS0-DJ-F

I replaced HDD to SSD, and want to also upgrade the RAM memory (3GB is pretty low, when using for example Android Studio, etc). I have some doubts, what parameters are needed to successfully upgrade it.
As I see, current (original) RAM is 1333MHz, and 7-7-7-20 (?). But on the intel site i see that it works with 800/1066. So it is probably underclocked.

Which RAM will suit me? What is important? Timings must be the same? What else?

I want to upgrade it to 6GB (leave current 2GB and buy 4GB, or buy 2x4GB, as I guess, that I can use only 2 slots)

Here are some pictures from CPU-Z:

CPU-Z pictures of laptop components (imgur)