Upgrading digital source device is not easy


I am looking for recommendation for upgrade from Cary 306 SACD professional.

My current set up is Harbeth 40.2/Cary 805 AE/ Cary SLP 05/ Cary 306 SACD professional plyer
I am using MAC/Amarra 4.0 /  Halide Design S/PDIF Bridge USB-S/PDIF converter via coaxial input to CAry 306 sacd professional. Rega P8.
I am wondering what would be good upgrade for my digital end.
I have a lot of SACD and CD collection and I have 2t byte music digital file.
I want digital end upgrade but I have no confidence to have better sounds after upgrade  since this Cary 306 SACD Professional is really good one.
I will appreciate some recommendation.
Thanks


zone5
avlee, thank you for recommendation
I think I will go with 2 box solution.
I am listening to digital file 80% of time for digital music.
What I am concerning is that upgraded DAC might not be better than Cary 306 SACD pro as DAC.
I feel necessity of new DAC but I am not sure which one will be meaningful upgrade from my current set up.

Post removed 
Post removed 
If I hook Cary 306 sacd pro to new DAC for CD vis digital output, can I still use this SACD player's analogue output to feed my preamp for SACDs without disconnecting digital output ?