Don't waste your money. Upgrade the bios and then go at a local shop that does repairs. Tell them i need ram and you want to see if it supports the 4gb sticks. They should have some open there to test.
Anything else will be a waste of your money and it's a shame if it actually supports the 4gb sticks and you get 2gb sticks. Now if you want to risk it and believe 4gb rumor is true go with the Crucial memory
@rupeshjoshi62 suggested.
Btw ram speed is rather irrelevant number. It doesn't change anything significantly except in apu and integrated graphics for low budget "gaming".
The problem is that in my country we do not have that electronic advantages and it will be impossible to find a memory stick that suits my PC here, I am buying it from amazon because I am going to travel and that's why it would help me, any electronic is very expensive here.
If I buy the 4GB and if it doesn't works, I am risking to loose my money because:
1. It would be extremely hard to find someone that sells appropriate memories for my PC in my country.
2. If there was, surely it is
twice the price you buy on USA or the internet.
3. If my PC has an error attempting to upgrade BIOS, I do not have a local repair shop I trust, if I go to one probably is that I attract robbers if they see me crossing the street with a PC, and these "repairers" have the electronic knowledge of a 5 years old and they can even finish killing my PC.
I do not want it for Gaming, I just want more because there is not enough RAM for my apps or even Windows 10, plus the annoying Cortana is there eating my memory, and my mom saying her PC is faster than mine and if she could she could throw it to the window because a turtle is faster (which I really don't understand because it is not that slow)