I want to make a home NAS PC and have an option to buy cheap (like in lines of 10-15€) HP PC:

1. HP 280 G1MT (4GB, i3-4160, 180W, 3 SATA slots) from 2016
2. HP Pro 3500MT (4GB, i3-3240, 300W, 4 SATA slots) from 2015
3. HP Pro 3500MT (8GB, i5-3470, 300W, 4 SATA slots) from 2014
4. HP Pro 3500MT (4GB, G645, 300W, 4 SATA slots) from 2012
5. HP Pro 3500MT (4GB, G640, 300W, 4 SATA slots) from 2012

Don't really care for the attached storage, I would probably buy a 2x 6TB or 2x8TB HDD and boot the OS (OpenMediaVault) from a USB stick (I would have 2 USB sticks with 1:1 config on them in case one USB dies).

Which one of the HPs would you suggest? (I would prefer the 280 G1 as it's the newest hardware wise, but I'm kind of afraid that the attached 180W PSU isn't enough if I would increase the amount of HDDs in the future plus it only has 3 SATA slots so I would quickly need to buy a PCIe<>SATA adapter...)

Or is there something that I don't see at the moment that would make choosing one of those PCs in the long run as a mistake?

Thanks