I thought about nas but I just don't see me needing to access all my files at the same time so one drive at a time is fine.
I just want a little box which can run a VM or two and can access some storage. For most things, one drive would be fine though I'd probably get at least two and mirror them. The VMs I would put on this guy would be low-impact things like a domain controller and a Vent/TS server, so storage capacity or even storage performance isn't overly critical. My next box will have at least 16 GB of RAM and maybe 32 GB; that's where all the beefy VMs will go so I can use them for development purposes.
I don't anticipate making this change for another year. My server was built with a 5 year lifespan in mind and by God, I'll use it for 5 years or more unless it explodes. When I kick my friend's dev lab off of it next month, I'm going to move the SQL VM from my HTPC over to it and I imagine I'll see a big performance improvement. Which reminds me, I need to email him.