Currently I'm running my PC with a i5 4590, GTX 970, and 8GB of RAM, with a 250GB SSD, and a 1TB HDD.
In one of my videos I was editing an AMV and although I set the video quality to a quarter, the framerate was around 5fps and wouldn't budge.
This has nothing to do with the RAM or any other hardware for that matter. If you search the forum, you will find enough threads that cover this subjects and from the endless bugs in AE CC 2015/ 2017 ever since the new preview mechanism has been introduced to wrong preview settings to specific issues with your footage and CoDecs this could be anything. You have not offered any info on that, so we can't advise specifically, but perhaps you can figure it out based on these clues. Otherwise you have to provide more info about your comp settings, items and effects used, preview settings and so on.
You shouldn't edit in After Effects. It is not built to edit. You should edit in Premiere Pro.
After Effects is made for motion graphics, compositing, and visual effects. And, as such, it handles video very differently from an editing program like Premiere Pro.
After Effects caches things first before it can play them back at full speed. It is possible what you are experiencing could be improved, but without knowing more about your project (as Mylenium mentions), we can't know.