Is this just a media sever or will you use it as a everyday PC?. If just a media sever you will not need a ssd for the os, you will not be driving the os so hard that it will need the speed of ssds. You should partition the drive into 2 drives so if need to rebuild, all data in the second drive should not be touched and only touch the os.
It's my HTPC. I have around 50TB of movies/tv shows and I use it for occasional gaming via Steam. So far, I hadn't had any issues with load times that have bothered me.
I don't have any data that I can't replace so I'm not concerned with RAID or anything like that, so I'd rather not partition. I was mainly thinking that I could use the 4tb drive I already had to save some money and use the extra space to download all of my Steam games on one drive for use with Big Picture mode.
It's used for XBMC 90% of the time though.
Provided your motherboard is new enough to support booting to a drive greater than 2TB, as Mrkazador said, you will be fine. I personally highly recommend an SSD instead. I have a 250GB one in my gaming machine and have several games, plus the OS and all the assorted other things (flash, java, etc) and still have a LOT of space left.