I have an Alienware PC that I bought back in 2015 and I’ve upgraded the GPU a few times. I’m wondering what other upgrades I could do such as CPU and ram or upgrades cooler. The computer performs amazingly still after 5 years and keeps up with every game that has come out playing at 1080p. 

My specs I know off hand: 

CPU: i7-5820k

Stock CPU cooler. I have 2 fans on the radiator in a push pull config.

I have 3 front fans that are the stock fans.

I'm putting in a MSI GTX 1660 6GB Ventus OC 

I have 16GB 2133mhz 4gbx4

875 PSU that came with the PC.

I also have the most recent bios 14 

Thank you in advance