To be honest I do not think that the Onix transport is the right one for you. Why?
Firstly, you mention that you own CDs but not SACDs. You therefore do not require a SACD/CD transport.
Secondly, Vivaldi is designed as a system. Whatever the combination of units it is important that they are in synch. That means that the same clock reference is sent to the units. If you want to learn more, find the FAQ on clocking ( FAQs will be transferred to the dCS Only the Music website next week). A silver disc transport must be able to receive that common clock reference. This requires a transport with a wordclock input and the Onix does not have this.
However if, as it seems, you only require CD support then the alternative below has a wordclock input and could be cheaper than the Onix. However you have not provided details in your profile of of where in the world you are and this may affect the end cost.One of our members ( another Vivaldi owner) has purchased one as seems very pleased on all counts:
Of course a source of the wordclock signal is needed. Ideally this should be Vivaldi system clock but I appreciate that it is costly and may not be what you are thinking of now. However, Vivaldi DAC does provide a wordclock output but I am wondering if and how how this can be used to supply both the transport and Upsampler. So I am tagging @AndrewS as if it is possible he has far more expertise than me on this.
Third party clocks cannot be guaranteed to conform to dCS standars and need to be able to produce and distribute 44.1 and 48kHz signals simultaneously or automatic synchronisation of tracks of varying sample rate bases is not possible. A real issue when using streaming services.
Let us know how you get on.