I strongly encourage you to get an SSD. They're terrific.
You say you need a TB or so. If you don't want to spring for a 1TB SSD, think about maybe getting a 500GB SSD and augmenting that with an inexpensive USB external drive. I doubt you really need to have a TB of blindingly fast access.
At 100.00 just for 250gb they are too high. Right now i am hoping to get another mobo as i think i broke mine, or the cpu, trying to get the heat sink (cleaned it) back on the ASRock 970 Extreme 3 i had.
I did it many times now but all that happens is that it begins to boot but i get nothing more than a black screen, and no HD activity.
For less than the price of a 120GB SSD (56 .00) one could get a pretty good Micro ATX mobo http://www.newegg.com/Product/Product.aspx?Item=N82E16813128565
But I do think 120GB is enough to install Windows 10 on. Put the data on another, though that still means slower access times for that.