I'd be really interested to know how that Cyrus CDi performs with the SU, and how the two differ, i.e CD vs streaming rips on SU. I had a Naim / Cyrus combo for a while before deciding to go all Naim, and it was an impressive performance, especially considering the price of the complete system as was, but just didn't quite work for me. Naim source and Cyrus amp was too airy and polite for my liking; lacked a bit of oomph and solidity. And as oomph at least was something the all Cyrus system didn't lack at all, I concluded that most of the bombast came from the CD player. Since matching with a Naim amp the energy and enthusiasm is great, which lead me to suspect that a Cyrus source with a Naim amp would be somewhat over powering. That was a much older CDP though, I had a CD8X which was released well over 10 years ago.
I have nothing but good things to say about the SN2, and general opinion seems to indicate a significant improvement vs the SU, so that combined with a CDX2 should be lovely, but as already suggested not convinced it would be a great match for the CDi. 272 with a 250 would give great flexibility, but if CD is to rule in your camp, a dedicated pre would probably give better results and VFM. Plus, if streaming is a nice-to-have, but very much secondary, there are relatively inexpensive ways of having that on the side, but with a noticeable, though not embarrassing, compromise in sound quality.
Then there's just speakers to worry about, which is an unfathomable minefield of differing performance, and disagreement on what works. Good luck with that bit.