I'd agree with all that. Noting that:
1. If you're preparing for 10G externally then you'll want a router with 2 x 10G ports. (*)
2. Cat5e is rated to run at up to 2.5G. If the link from upstairs to downstairs is short then it may just about work at 10G (and good-quality Cat5e often exceeds Cat5e specs). But ideally you'd either replace this with Cat6A, or a single-mode fibre patch lead if the router and switch both have an SFP+ port. (It's better to avoid copper 10G SFP+ modules if you can, as they tend to get very hot. And SM fibre will allow speeds of 25G and above in future). (**)
3. You didn't say what model of Unifi AP you have. For 2.5G uplink you'll need something like U6 Enterprise, the new U7 Lite (which is cheap but doesn't have 6GHz), or the U7 Pro or above. For 10G uplink it's the U7 Pro XG/XGS.
(*) In general: I suggest delaying any purchase as long as possible, until it's actually needed. You'd kick yourself if you bought something now before you needed it, and in a year's time you could have got something both better and cheaper.
For the 2.5G router, would you consider a NUC-type server with 2 x 2.5G ports? I bought the Beelink EQ12 16G/500G on Amazon for £240 a couple of years ago and it's a very nice low-power N100 (4-core) box, although I use it as a server rather than a router. It's the kind of thing you could easily re-use when you later upgrade to a more powerful 10G router.
Note that you can buy a RouterOS licence to run on PC hardware - the price is
very reasonable - or as a VM (they call that CHR - Cloud Hosted Router). Basically, build your own Mikrotik.
(**) If the downstairs router isn't doing anything other than routing (i.e. you're not using its wireless capabilities or any other LAN switch ports) then you could move the router up into the loft, and use the Cat5e cable just to connect down to the ONT. That allows you to keep the 2.5G uplink for now, while upgrading everything else to 10G
Have fun!
Edited by candlerb (Mon 05-May-25 10:56:45)