Ive just bought a Cimbali Junior s1 (pourover ie not plumbed ) and if all goes to plan it will eventually replace silvia.
No real compeling reason to upgrade, Im very happy with the quality of silvias output and dont expect a qantm improvement in taste although volume production when required should be much easier. Im also hopeful of greater consistency between shots but this may well be fantasy!
The Cimbali is second hand, thus I had no choice for plumbed or not plumbed, however depending on the price difference I may well have selected the same model. You always have the option whether via a manufactrers kit or DIY to convert to plumbed in anyway.
Good luck, I rather liked the look of the S24 as well. Have you seen the Oscar sienna are clearing for under $1k? Cheapest HX option by far for a new machine.