Worth Replacing 8gb Mem to 16Gb?

No
Most games use 2 gig of memory or less. Some can use up to 4 gig for ultra textures etc.

16gb can boost up your pc well if you want to do some extra stuff like photoshop,editing etc but it gives you about 10%performance in gamming.

If all the available ram is superior than the game max memory usage coded in it, it's simple IMPOSSIBLE to get any performance gains.
So this 10% gain is completely irreal, and random.

Few games uses more than 4gb. So I would say 8gb is more than enough if you only gaming.

I, however, only do gaming and have 16gb.
So you guys would ask: Vitor, why do you have 16gb memory?
Answer: Cause just wanted to piss off some friends saying I have more ram, and I had money at the time to burn in hardware.

Unless you do Photoshop or Video Editing. you dont need more than 8gigs.

8GB is aplenty. No need to upgrade now mate.

8GB for gamers, 16GB can actually harm performance on some titles.
Open as many programs as you may have open while gaming and check Resource Monitor. That will give an idea of what you need.

I'd stay with the 8gb, unless you do alot of photoshop. Recently I bought 8Gb because it was on sale so I stuck those in and I had an extra 4Gb laying around.. so i ended up putting that in as well. I did no notice any performance boost.

No its not worth it. Stick with 8GB.