Is it possible to add fastest internal Hard drive in Dell XPS 8300

I am the long time user of Dell XPS 8300; there are many best features I have seen in this Desktop. I am happy with this Dell Desktop, but however recently I have decided to add one fastest internal hard drive into my system. So I just want to know whether it is possible to make some extra addition of such Hard Drive in this Dell XPS 8300. If yes then how? Which one should I prefer for this? SATA-II hard drive or any other hard drive, which will compatible with this system? If you guys have any ideas then please let me know.

The fastest Hard drive that I know is SSD, and also any rotating disc drive will also provide the same feature. There on the XPS 8300 motherboard the first two ports are SATA III and the other last two are for SATA II, so for that reason it is possible to install SATA III hard drives or SSD to the first two ports.