X51 R2, upgrade help, which parts?

Hi, 

I bought my Alienware X51 R2 in late 2014. I'm pretty pleased with it but I think it needs some upgrading - most of all, because it starts to be slow and noisy while gaming.

Games I play: FM20, LOL, WOW, CS:GO, Total War series
I use it for photo editing as well - with Affinity Photo

I could really use some help finding parts worth replacing.

- 8GB Dual Channel DDR3 at 1600Mhz
- NVIDIA GeForce GTX 745 with 4GB DDR3
- 1 TB SATA med 6 Gb/s (64 MB cache) and 7.200 revolutions/min
- 4th Generation Intel Core i5-4460 processor (4-cores, 6MB Cache, up to 3.4GHz w/Intel Turbo Boost

Advice is appreciated!