here's a general advice page on improving performance in Ae: Improve performance in After Effects so make sure you read through.
system resources look fine but without knowing what you have in this project we can't tell you much. many things could make your workflow inefficient, and sometimes it's is just too resource intensive you have to bare with it. show us a full screenshot of your Ae interface, if you can send a video capture of the performance you are experiencing.
Do you often delete all your caché and temporary files? Many Adobe users don't know about the existence of this. Maybe you'd like to have a quick look to this video, you might find it helpful. Get Rid of your Adobe Caché and Temporary Files!! - YouTube
Make sure your layers and compositions in and out points are trimmed so the layers are only being computed when they need to be. Make sure AE is not computing layers or comps or effects that aren't being seen. Not doing this can slow AE to a crawl.
Did you ever get your performance issues ironed out? Please let us know what helped, if anything.