so thinking about my desire for a new NAS.

Its main job is gonna be SMB.

(I could run a fuckload of services on it 'cos it's there, or I could just not do that.)

I think our network already tops out the anaemic Marvell CPU in our 2015 Synology, lol.

so I guess I'm interested in (1) can fit lots of SSD (whatever form factor) (2) good I/O, moving bytes to/from network fast enough.

I suspect any box with a non-anaemic CPU and enough slots would probably do the whole job.

also it's gotta be silent or nearly.

So what springs to your mind?

@davidgerard Had a bout of NAS desire recently myself and would've bought a Unifi UNAS Pro, but ran out of NAS interest before spending money. Upside: cheapest 7-drive NAS with 10G networking that I know of, and it's a well established company. Downside: if you expect a NAS to have all the software features of a Synology, this isn't it. It's Unifi's first NAS, and they've chosen the path of rolling out features over time rather than trying to launch with everything.