I use:
a 840 Pro 256GB as a boot drive+few programs i use heavily (like GTA4 or SR4)
a 2TB Barracuda (ST2000DM001) for general storage for practically anything
and a 1TB Barracuda (ST31000528AS) which I ext racted from an external drive simply because it looked too clumsy/not clean with the wires spewing out.
I use these in my main rig, I still have about 30GBs left on the SSD but that 1TB is filled and not much is left on the 2TB either
I also bought the 840 Pro, simply because i was told it was the best ssd i could buy (not ultiately best, but you get what i'm saying) and the 2TB one was offered by the salesman (i know, i know) in the computer shop over the WD Green, which i later learned out to be a drive which can fail more and is slower.
for once the salesman was correct
Link to an external site (OCN) http://www.overclock.net/t/1425999/linus-win-8x-wd-red-4tb-drives/0_100
good luck to all!