Can not speak for the Cambridge CXN V2 but I’m sure it’s a fine player for the money. I do own a 851C and for several years I used its DAC over the DAC in my BS Vault 2. I’d be surprised if the DAC section in the CXN V2 surpasses the 851C, but I can tell you, to my ears, my RME ADI 2fs DAC is much better than the DAC in the 851C which is very good mind you.
No idea if the streamer part of the Cambridge is better over the Bluesound Node 2i, but I suspect it is, as it should be for the cost difference. When I compare CD’s I have ripped to the Vault 2 to Tidal or Qobuz, the ripped or CD clearly sound better which has me looking at upgrading to others streamers; that being said, if I was not using the RME/Pardo, the difference is not noticeable when using the DAC in the BS.
As mentioned by others it’s all subjective to your ears and system. You mention the ModWright mod to the Cambridge but that’s adding another $1,500 to the cost of the Cambridge, and maybe it’s a great upgrade, that I don’t know but the cost of the Cambridge/ModWright is pushing you over $2,500 I think. For $2,500 I’d probably think hard at keeping the Node and buy a higher end DAC. As mentioned by many in a lot of post elsewhere, I agree the DAC makes more of a difference over the streamer, and spending more money on a streamer will make no difference if the DAC can’t back it up.