I’ve also upgraded my old Marantz cd player and Audiolab is superb transport. The detail it extracts from the cd is remarkable. The sound is very detailed and has fantastic dynamics.
I’m very impressed for the money.
In theory if you are using the player as a transport only you shouldn’t hear differences between the sources. If you have used analogue outputs of the player the differences you hear are between the DAC in the player versus that in the SA30…. (assuming decent shielded cables of course, and by that I don’t mean “snake oil” pricey stuff 
)
I have a cds50 connected up with both analogue and digital outputs to the SA30. Overall with digital I feel it’s just a tiny little bit brighter and the volume level seems higher than analogue, both are good.