Right now, I am looking to make some upgrades to my PC so that I can play a heavily modded Skyrim (and other future releases). After the installation of Skyrim Flora Overhaul, my machine has the occasional low FPS hiccup.

However, at the moment, I can only choose to upgrade either my CPU or RAM.

Right now, I have an AMD A4-5300 (3.4 - 3.6 GHz) and 6GB of RAM.

Should I upgrade my processor to something with more cores and the same speed, or should I bump up my RAM to +8GB?

If you're planing the upgrade for Skyrim, i highly recomend you go to Intel CPUs as they run Skyrim much better than AMD. I bought an AMD FX 6300 and am a bit disapointed with the performance on cities. Overall its a good and cheap CPU that will run most of your games at 50-60fps maxed.

Going from 6 to 8Gb will not make difference in fps for you, so i recomend you update your CPU.

Clamp your Frame Rates to the 40 to 48 range and you will never notice these FPS drops.

Upgrade your CPU and GPU if necessary. But I wouldn't put too much money into it if it's only for Skyrim. Have a look at this thread over at the STEP forum: http://forum.step-project.com/showthread.php?tid=3319.

In short, the Skyrim engine can only handle so much before it crumbles. It doesn't matter if you have a computer that costs a million dollars.

So use 1024K textures and not too many mods, is my friendly advice.

Btw, the sweetspot memory-wise seems to be 8GB nowadays. You won't need more in todays games. And you won't even need that much in Skyrim, since it has the infamous 3.1GB RAM limit.

Now i really noticed that you said "After the installation of Skyrim Flora Overhaul, my machine has the occasional low FPS hiccup..."

In this case, a CPU update will not help you since Flora Overhaul is a GPU intensive mod. If you're planing an update because of this mod you should update your GPU.

You should be asking that here instead:

http://www.gamesas.com/topic/1482033-the-community-tech-thread-no-134/