Some components too old now?

Thanks for all your comments. Boiling it all down, it seems that the only thing I should consider is potentially changing my Aragon DAC.
Does anyone know much about the Aragon D2A? It has a separate power supply, and I remember that in its day it was considered one of the best.

Like you said, it was one of the best in its' day, but that was more than 20 years ago. I think you'll find just about any DAC built recently will be a significant improvement.
I found a link to another forum (hopefully allowed) asking the same question:
https://www.audiosciencereview.com/forum/index.php?threads/dacs-old-vs-new.3229/
B

Hmm. Thanks gdnrbob - really interesting.
Reading that thread, and over-summarising again, it seems as though a really good 90’s DAC (like the Aragon) will still sound as good as a decent modern one, but the difference is a modern one will have far more functionality. 
Is that the way you read it?

I dont know those specific components well, but in general i agree with Eric and others.  The preamp is probably fine the DAC likely can be vastly bettered ( and Schiit is a great place to start). I can't speak for the Marantz, but bear in mind that SPDIF is NOT, repeat NOT, a purely digital signal - no time to go into why, by you need a low jitter output.
A new DAC with USB and/or network in also lets you move toward the future, which is streaming.
I am constantly amazed that stuff that was great 30 years ago is often still great. But not digital.
G