Not really sure just where you are going with this one Phil??
You don't want to run headless... but in reality picks 1 & 2 are designed, mainly,to be administered via web GUI. Once installed you open up your fav browser and log in and away ya go.
If your trully going FreeNAS 8 and ZFS your going to have to chuck a serious CPU AT IT AND MEGA BUCKETS OF RAM to get any sort of decent transfer speeds. Most of the "yeah it's great" comments are flyng in from people that have run it in VB or some virtulaised setup in small lab setups and no real hardware hammering behind it at all. Just watch the Youtube , and such like, demos... it's all VB and full of c^^p. Bottomline .... is that FreeNAS 8 is aimed squarely at enterprise level use and hardware
OpenMediaVault.... well the poor mans FreeNAS 7 really... still struggling to get up and take it's fist wobbly steps. Yup... full of features but unless you have a really good grounding in using something like FreeNAS or FreeBSD your going to struggle to get most of it to behave.!! After using FreeNas 7 until swapping to OpenMediaVault... frankly I'm giving it another week and then I'm going to whack 7 back on
If you have the hardware to support a full 7 - 9TB's of data in a RAID 5, 6 or 10 , ZFS or it's incarnations.... you already have the time, money and inclination to think ahead and have that redundant server in place already