I'm using an i7 (2nd gen), 6gb ram, NVIDIA GeForce GTX 750 (2GB video ram), 1.5tb HDD. It handles all my games at near or full settings, and handles the Oculus Rift with minimal latency. All of that minus the video card was an out of the box machine from Staples, the graphic card was from Future Shop (Absorbed by Best Buy). Acer, not all that expensive. In fact, I have an Acer Iconia tablet that is actually just shy of your specs, swap the HDD for SSD of (EDIT) just shy of half your capacity, and I can't recall the graphics specs but not quite that good... Does run Stick of Truth flawlessly though!
I'd go for a new computer personally. I'd like a new one myself! There is a limit to how much a RAM upgrade would improve performance.
Check out this site, play around, build your "dream PC". It is good for checking compatibility and not allowing you to screw up (as easily)! The last dream PC I created would cost about $8000.....
https://pcpartpicker.com