Greeko85 :
You can upgrade your cpu up to a 6700t. When you're playing whats your limiting factor? Can you monitor your cpu and gpu usage? You may benefit from a gpu upgrade as well but that will probably requiring upgrading your psu as well which could be a bit of trouble (I haven't worked with any alienware products so not sure if they use proprietary connections/sizing restrictions).
While im playing Black ops 4 my CPU is at a constant 80-100% usage when im playing on the lowest resolution possible, as told through Task Manager, while my GPU is at around 10-60% usage.