Last time I asked around on 2.5G ethernet I was told to skip it and go to 10 Gigs straight as its “cheaper” and better than 2.5G. So I started to investigate and I am baffled by the costs. Let me break it down:
Quality 10G switch Mikrotik CRS305-1G-4S+IN ~150 $ (this seems reasonable)
10G SFP+ RJ45 modules - these are starting from 50$ on ebay from china which seems excessive, given i would need at least 4 of them.
10G NIC -Intel X540 T2 for around 40 $ if I want to go with RJ45. X520 with SFP+ connector can be had for 30$ but does not seem to worth it, given then price of SFP+ modules.
So I am somewhere around 430 $ for connecting my NAS and desktop PC via 10Gig. Compared to that, I can upgrade to 2.5G only for approx. 80 $
I could partially go with fiber instead of copper, pushing down the SFP+ module costs to 15$, but i still need at least one RJ45 module to run to my home PC. Also I am concerned fiber will bring some additional complexities that I am not prepared for (have zero experience with it).
Get as much core infrastructure stuff as you can with SFP(+ or 28). Uses DACs where the lengths dictate (fairly reasonably priced) and transceivers/glass where you need further runs or confined space pulls to other rooms. Where you absolutely have to go with copper transceivers. For example, the only 10G I run at home over twisted pair is from my synology to my distribution switch. I only have one workstation that runs multigig which is my editing/gaming PC. Everything else is gig so no worries.