Not critical to be virtualized, but once you understand the benefits, you will love it.
If you go for virtual, you do not need to run 3 separate instances. I will base it again more if how many snapshots or rollbacks you might need. If none, and you have other management tools built in, even 1 would do for all. Or in that case then, maybe even no VM.
Another 2 reasons i like VMs:
1. I can move them around as needed. When at home, the VM resides on the server and i dont use resources on my main work laptop. If traveling and I need it with me, i can move it over to the laptop.
2. Server configs can be a chore. Reformatting and reinstalling for an HTPC is no big deal. Yes you can make images of the whole machine to roll back to, but again, selective restoration wont be simple. With VMs, i set it up as i want it, and archive the files away. More snapshots does mean more storage space, so i do not keep more then 2 or 3 at a time.
As for media drive speed, there are enough debates out there, but with most modern drives, there is no much difference in sound, power usage or performance. It usually boils down to what is the best deal out when ready to buy. And of course, have backups!