If you only want to listen to Tidal/Amazon, and you already have a Node, buying the Vault doesnt make sense. The Vault does 3 things: 1) Rips and stores CDs 2) acts as a streamer for services such as Tidal/Amazon, Internet Radio, or the aforementioned ripped CDs 3) is a DAC.
The Node does 2 and 3.
In your case I would blow the budget on an external DAC to best the DAC in the Node. If you later become dissatisfied with the Node as a streamer you can upgrade it, but presumably you must be happy with it since you are considering getting a Vault