Thanks John, yes good spot. I completely meant Parity drive and not cache drive in my OP. D'oh!
Looks like the ASRock 970 extreme3 is the most affordable option for the virtualization stuff, I must admit I had only briefly glanced at the requirements there, so thanks for pointing that out.
I'm now wondering if I should just ditch the virtualization stuff and save it for another build later down the line. I've seen that some people run the apps/plugins from cache drive. Is that a safer way to protect against data loss so the storage drives aren't touched? I don't like the idea of having running applications on my NAS - paranoid the disks might die! Maybe incorrectly so.
The other option is to sort out a raspberry pi I can borrow on permanent loan for free with the usual sab,sickbeard,couchpotato and reduce the components in the NAS.
Any recommendations what sort of CPU I'd be needing for just streaming to xbmc boxes/reading and writing relatively quickly for file transfer and how that compares with the bare minimum for Plex? I am now wondering if I'm over powering the build for no reason, if I take off the virtualization requirement.
Cheers,