Want to upgrade RAM in Acer Aspire E17, not sure what to buy

[InfinityRider]

Looking to upgrade the RAM in my Acer Aspire E 17 ES1-711-P75P

This laptop currently has 4.00GB DDR3 666MHz (9-9-9-24).
But it has only one RAM slot and the max is 8GB.
So I am looking for a 8GB stick but I haven't bought RAM before so I want to make sure I buy the right one. I tried looking for a 666MHz (9-9-9-24) stick but I couldn't find one, so now am I unsure what to look for.

Can I have some help finding the right RAM. Thanks.

Edit: Found some compatible Crucial and Kingston RAM

Which would be better to buy:

http://www.ebuyer.com/581451-kingson-8gb-ddr3-1600mhz-sodimm-1-35v-m1g64kl110
http://uk.crucial.com/gbr/en/ct102464bf160b
http://uk.crucial.com/gbr/en/ct102464bf186d

The Kingston and the first Crucial have the exact same specs and are almost the same price. CL-11 and 1600mhz.
The second Crucial has CL-13 and 1866mhz and costs slightly more.
Just read up on it and lower CL is better, but higher mhz is better, so now i'm not sure if i should go for the more expensive one or not.

 

[blurryy]

Memory is something you don't want to cheap out on.

This is steal for the price / GB. : http://www.newegg.com/Product/Product.aspx?Item=N82E16820231342
Your looking for a maximum of 8GB DDR3L SDRAM.

Let me know if you want a different brand for RAM, but 48.99 is a steal for what you get.