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
Post removed 
Thank you.
I am also thinking of adding DAC instead of SACD player.
My question is which DAC will be worth it to upgrade from using Cary 306 SACD pro as DAC (that is my current set up).
So..... Please give me some recommendation.