SSD for OS definitely, For data I'm not so sure.
I had, previously, Terabyte Raid HDD's, which I found I rarely used.
DVD's, Music, Photos etc.
Plus big HDD for OS (Dual Boot Win7 and Linux).
However I found
Win7 plus browsers and OpenOffice etc. fit fine in a 32GB SSD
Linux you can run same in 8GB.
Both run very fast, no failures to date, simple precautions only.
External USB HDDs are fast enough to stream films from, and keep backups.
I think, unless you are a gamer or heavy Photoshopper (or Gimp) maybe you don't need TB of HDD.
Just running your OS from an SSD will give you a significant performance boost.
Will be much, much cheaper, and these days (unless you need the latest hyperfast kit), cheaper is good.
Regarding (re)installing software.
I just gave up trying to reinstall Win7, it took forever, next day I was still downloading updates.
I don't hate Windows, I just don't have a compelling reason to want to pay for it.
I quite happily use it on my wifes laptop.
Linux I can download, install, update, and add programs in 2 to 3hrs.
Odd Windows programs I can run under WINE.
Win8 (maybe) will be easier to install, but I am not happy at the prospect of a board that "only" runs Win8.
So buy a smaller SSD and give it a try with your OS of choice.
Buy a Linux Magazine and try a Live CD/USB.
Have fun and save money.
gvnmcknz