Thanks for the fast reply!
I have 2 old NAS actually, a D-Link 310 something, it no longer supports most recent version of SMB (Only v1.1) so that got retired. I also have a single bay Buffalo 210D (2TB)
I'd like to get a 4+ bay NAS so I can had some RAID Resiliency and would start of with 32TB of space so I can point all my PC's at it.
The reason for the memory upgrade and SSD cache: I'll be running at least 2VM's from it, so the more memory the better (16GB - unofficially supported) and I've seen many reviews stating the SSD cache comes in really handy when using VM's.
I also looked at the older DS1715+ as that has 5 drive caddies - 4NIC's and PCIE expansion port but the weaker process, lower amount of RAM and higher price put me off.
Just a shame the DS918+ only had 2xGbE - I would have liked a 10GbE!