Do you need 4TB for your games? I have 2x2TB SSDs, one is my Windows installation with quite a bit of games (500GB free) and the other is just videos, music, documents.
In Germany, I could get a 500GB SSD for about 50€, 1TB is 90€ and 2TB is 200€. That 200€ is the price for the Primocache, RAID...