SSD vs GPU for After Effects

[J Zimm]

Previews in A E run at full res at around 8fps and I would like to increase it's speed.
Here are my current specs.
i7 4770
16GB Ram
1TB Hdd with OS and Media
250GB HDD (old) with Cache
Radeon HD 7570

I am looking to upgrade either to a gtx 950 FTW or an 250GB ssd like the crucial bx200 or samsung 850 evo.
What option would result in the greatest performance increase?

 

[k1114]

Ssd. Previews render by the cpu as well as the final render. There is very few gpu acceleration other than mostly the viewports themselves.