*Please specify what you mean by "server"... to play videos?
Not sure 8GB is needed to upgrade a computer for basic tasks.
My dad's laptop only has 2GB and it runs quite well. He uses it only for e-mail and browsing though we've streamed HD content both through wi-fi and HDMI from the internal HDD. I've used it myself and it's not much different from my 16GB gaming rig.
4GB might be faster but hard to say since this is pretty basic. It's not quite clear exactly how you are using it, and how often. It wasn't until I opened a lot of TABS and started multi-tasking that I noticed a slow-down. Again though, I booted up and used a web browser just like my gaming rig. Only boot times were different.
An SSD might be something else to consider. That made a noticeable difference though the laptop HDD was quite slow.
Again, I'll probably get some flak but for pretty light usage I'm not sure more system memory will be noticeable.
Options:
1) Upgrade to Windows 10 (free) once released.
2) Upgrade to 4GB. I think 8GB is a waste of money for this use.
*I have 16GB of DDR3 memory. I booted up my system, checked Outlook e-mail and have about ten tabs open in Firefox and have 2.7GB used. 500MB of that is Firefox. 56MB is Battlenet (Diablo 3). 76MB is the NVidia Control Panel (really NVidia?).
3) Buy an SSD and clone with Machrium Reflect or similar (see pcpartpicker). Once done make a backup Image such as Acronis True Image (SSD to HDD).
You might even find Windows 10 is snappier with the same 2GB of memory though I'm not certain. I thought I read somewhere it was being optimized to use slightly less system memory.