Thanks everyone of your replies. Sorry for the delay. was waiting to get an email for new responses. Dunno if I missed to subscribed to the thread. Anyway:
Point is, I want to use the hardware I have laying around here. Otherwise I guess I will pump too much money in this project. I agree that a i3 or i5 would be too powerful and power consuming for an OMV, but offers the option for later upgrade to an NextCloud. I like the idea of assembling an ITX with an Pentium G. I think for me would be best to assemble an ITX in a not too big case with silent fans. Then I would be flexible for later upgrade (maybe I want to powerup the system to a whole server, when I build up more linux skills.) Any suggestions in that direction?
Thanks alot!