Well, A SSD will shred any HDD around and that means booting at around 10 seconds and very minimal loading times for applications. Also loading objects in games is much faster.
Samsung EVO Series 250GB SSD
You have an SSD already but go for more space, as you may find 120GB isn't enough to store the things you need on their at a time (My 256GB SSD is more then half full and only has the apps I need). the one I listed has a read of 540MB/s and read of 520MB/s, much better then the corsair one.
Other suggestions:
-upgrade your ram to 16GB
-Change the 4670k to 4770k (if this PC hasn't been built yet)
-PC Case, if you wanted a full tower (if this PC hasn't been built yet)