FSX PC Upgrade?

Hi, I currently have this setup:

Asus iv z68 extreme gene-z board

i2500k overclocked to 4,9 ghz stable

8gb gskill 1600mhz

msi gtx 570 overclocked

Samsung S27A950 27" 120hz

2 ssds, crucial m4 128gb and ocz vertex 3 60gb.

Im happy with my pc that i now have for 1 year. But in fsx with the ngx @eham and clouds the perforamnce is ok but not smooth enough.

I have some money to spent but not enough for a entirly new pc.

My question is: is it wise to upgrade to an 770 / 780 with 2133 faster memory? And is the fps and smooth difference between 2500k / 4740k big?

Thanks!