Hello again rye,
Just thought I'd update the thread to say that I settled for the Celeron N2820 however I got the new N2830 CPU which Intel have replaced the N2820 with. Yay!
OMV is installed on an external USB3 SSD removal drive which sits outside on top of the case, and for data I have connected a 2TB 2.5 inch internal hard drive, performance is good and data read/write is faster than my old qnap!
Power consumption is also impressive:
Idle (disk not spinning) = 5 watts
Idle (disk spinning) = 7 watts
Data read/write = 10/11 watts
Performance of the NUC N2820 is very good with OMV although I'm yet to push the system as I've not yet installed plex, sickbeard and SABnzbd etc so time will tell but it can't be any worse than the old qnap.
I haven't installed Windows or OpenElec (don't plan to either) so can't comment on performance for any other OS.
I wasted a lot of time on this mini project and have made a mess (by ordering NUC i3 and other bits and bobs) but I'm finally very happy with the end result.
I really wanted to keep the NUC i3 but I just couldn't convince myself that it made sense for a single drive NAS especially when it costs about twice as much.
Also another benefit of the Celeron is that it uses a small power adaptor directly at the mains like a mobile charger (no brick) whereas the i3 version, I believe, needs a brick due to the extra power requirements.
I hope this helps other users in the future but please bear in mind that the Celeron only has one internal sata connector which means only ONE internal drive. Not ideal for a NAS but I'm making do with the external USB 3 for now.
It's also quite cheap (total cost about £140 for NUC and 4GB RAM, I already had an SSD and 2.5 HDDs which saved costs considerably) so in the future I can use it as an dedicated HTPC if needs change so it won't go to waste.
Oh and its whisper quiet and runs cool.
Sorry it's turned out like a mini review.
Thanks again for your time Rye.
Regards