Don't spend many hundreds for the TBs.
We'll agree to disagree on that one. That is why we had to just upgrade our main SSD from half to full terabyte, because just programs installed and their associated paraphernalia, ran us out of room on both iMac's. We would be constantly trying to recover room each week just to run the systems, hence larger was needed.Samsung's 850 500GB EVO more than enough for the OS, for some large often used programs and their data.
Thanks so muchGoogle SSD reviews to see the latest for what you want, price and performance, performance and don't care about price, so forth.
http://www.ssdreview.com/ssd-solid-state-recommendation.html may help you.
PCI SSD smashes sata connected types. I just purchased 2 x http://amzn.to/2bn4NGf a couple of months ago... and they're amazing for sequential read / write.
Samsung are really good too... I also run those in my synology unit. Just WOW for performance in a small business network. Honestly... you're probably better off with something like an external synology unit if storage is your issue.